CN115526955B

CN115526955B - Method, equipment and medium for generating cornea topographic map

Info

Publication number: CN115526955B
Application number: CN202211080683.7A
Authority: CN
Inventors: 陈海银; 于航; 王立峰
Original assignee: Hangzhou Weixiao Medical Technology Co ltd
Current assignee: Hangzhou Weixiao Medical Technology Co ltd
Priority date: 2022-09-05
Filing date: 2022-09-05
Publication date: 2023-06-02
Anticipated expiration: 2042-09-05
Also published as: CN115526955A

Abstract

According to example embodiments of the present disclosure, a method, apparatus, and medium for generating a corneal topography are provided. The method comprises the following steps: acquiring a plurality of first backlight loop images aiming at the same cornea, wherein the plurality of first backlight loop images are acquired at a plurality of positions in the preset eye axis direction by an axial stepping motor moving image acquisition device; determining the number of pixels occupied by the width of the backlight loop in each first backlight loop image; fitting the determined number of pixels to a parabola with an upward opening; determining the position of an axial stepping motor corresponding to the lowest point of the parabola; after the axial stepping motor is controlled to move from a preset zero position to the determined position of the axial stepping motor, a plurality of second backlight loop images of the target cornea are acquired, and the second backlight loop images have diaphragms with different diameters; and generating a corneal topography based on the plurality of second back-light ring images. This can greatly shorten the moving focusing time for the cornea.

Description

Method, equipment and medium for generating cornea topographic map

Technical Field

Embodiments of the present disclosure relate generally to the field of image processing, and more particularly, to a method, electronic device, and computer-readable medium for generating a corneal topography.

Background

Generating a corneal topography requires measurement of a human eye cornea signal. The traditional method is that an operator roughly moves human eyes to the center point of a camera interface through subjective judgment, then the user moves a handle back and forth to aim at the center point of the human eyes through the preset focal length position of a camera lens, and the optimal focusing position of the human eyes is judged by naked eyes, so that the efficiency is low.

In addition, the error of the front and back focal length positions determined by naked eyes in calculating the curvature radius and the pixel value of the edge focusing has a relatively large influence on the final result, because the calculation formula of the curvature radius directly relates to the number of pixels occupied by the width of the image of the aperture.

Disclosure of Invention

Embodiments of the present disclosure provide a method, electronic device, and computer-readable medium for generating a corneal topography that can greatly shorten the moving focus time for the cornea.

In a first aspect of the present disclosure, a method for generating a corneal topography is provided. The method comprises the following steps: acquiring a plurality of first backlight loop images aiming at the same cornea, wherein the plurality of first backlight loop images are acquired at a plurality of positions in the preset eye axis direction by an axial stepping motor moving image acquisition device; determining the number of pixels occupied by the width of the backlight loop in each first backlight loop image; fitting the determined number of pixels to a parabola with an upward opening; determining the position of an axial stepping motor corresponding to the lowest point of the parabola; after the axial stepping motor is controlled to move from a preset zero position to the determined position of the axial stepping motor, a plurality of second backlight loop images of the target cornea are acquired, and the second backlight loop images have diaphragms with different diameters; and generating a corneal topography based on the plurality of second back-light ring images.

In a second aspect of the present disclosure, there is provided an electronic device comprising: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method according to the first aspect of the present disclosure.

In a third aspect of the present disclosure, there is provided a non-transitory computer readable storage medium storing computer instructions for causing a computer to perform the method according to the first aspect of the present disclosure.

The summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the disclosure, nor is it intended to be used to limit the scope of the disclosure.

Drawings

The foregoing and other objects, features and advantages of the disclosure will be apparent from the following more particular descriptions of exemplary embodiments of the disclosure as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the disclosure.

Fig. 1 is a schematic view of a projection apparatus based on corneal reflection according to embodiment 1 of the present invention.

Fig. 2 is a schematic view of a projection device based on corneal reflection according to embodiment 1 of the present invention.

FIG. 3 is a side view of a projection disk in an embodiment of the invention.

Fig. 4 is a comparison chart of the output beam of the shaping module according to embodiment 2 of the present invention, which is used to show that the thickness of the hollow cone beam output by the shaping module changes when the diameter of the parallel beam received by the shaping module changes.

Fig. 5 is a structural comparison diagram of the light source module of embodiment 2 of the present invention under three transients.

Fig. 6 is a schematic structural view of a corneal topographer of example 4 of the present invention.

Fig. 7 is a schematic structural view of a corneal topographer of example 5 of the present invention.

Fig. 8 is a schematic structural view of a corneal topographer of example 6 of the present invention.

Fig. 9 is a schematic view of a projection device based on corneal reflection according to an embodiment of the present invention.

Fig. 10 illustrates a schematic diagram of an example environment 1000, according to an embodiment of the disclosure.

Fig. 11 shows a schematic diagram of a method 1100 for generating a corneal topography, in accordance with an embodiment of the present disclosure.

Fig. 12 shows a schematic diagram of a method 1200 for generating a corneal topography, in accordance with an embodiment of the disclosure.

Fig. 13 shows a schematic diagram for acquiring a region of interest for a placido disc aperture according to an embodiment of the present disclosure.

Fig. 14 shows a schematic diagram for elliptical detection within a region of interest according to an embodiment of the present disclosure.

Fig. 15 shows a schematic diagram of a search area according to an embodiment of the present disclosure.

Fig. 16 shows a schematic diagram of a constraint according to an embodiment of the present disclosure.

Fig. 17 shows a schematic diagram of a fitted ellipse according to an embodiment of the present disclosure.

Fig. 18 shows a schematic diagram of a method 1800 for generating a corneal topography, in accordance with an embodiment of the present disclosure.

Fig. 19 shows a schematic view of a right semi-meridian according to an embodiment of the present disclosure.

Fig. 20 shows a schematic diagram of a convolution result according to an embodiment of the present disclosure.

Fig. 21 shows a schematic diagram of gray values of a predetermined number of pixels according to an embodiment of the present disclosure.

Fig. 22 shows a schematic diagram of a fitted curve according to an embodiment of the present disclosure.

Fig. 23 shows a schematic diagram of calculating radii of feature points corresponding to cornea points according to an embodiment of the present disclosure.

Fig. 24 shows a schematic diagram of the spherical error.

Fig. 25 shows a schematic diagram of an arc length iterative method according to an embodiment of the present disclosure.

Fig. 26 schematically illustrates a block diagram of an electronic device 2600 suitable for use in implementing embodiments of the present disclosure.

Like or corresponding reference characters indicate like or corresponding parts throughout the several views.

Reference numerals

Light source mechanism 10

Light output end 101

Hollow cone beam 102

Light source module 103

First lens module 1031

Second lens module 1032

Third lens module 1033

Light source 1034

Shaping module 104, 104'

Projection disk 20

First side 201

Second side 202

Reflection unit 203

First surface 204

Second surface 205

First movement mechanism 30

Preset eye axis 40

Imaging module 50

First end 501

Second end 502

Spectroscope element 503

Through hole 5031

Imaging lens group 504

Image sensor 505

Reflected light 60

Cone lens 70 turntable 71 on shaping module 104

Detailed Description

Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are illustrated in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

In the description of the present invention, "structure" and "mechanism" are understood broadly, and "structure" is understood to mean a part or component, and mechanism is understood to mean a component. The "light source output end" is a virtual concept, and refers to the end of the light source mechanism, which is close to the projection disk.

In the description of the present invention, the "preset eye axis" is a hypothetical virtual line, which can be understood as a parameter set during the development and assembly of a product; in the application process, the actual eye axis corresponding to the cornea is leaned against the preset eye axis, and the cornea and the preset eye axis are overlapped in an ideal state, and the preset eye axis is represented by a solid line in fig. 1 and is used for intuitively representing the relative position relation of the cornea, the projection disc and the annular light. The lines containing double-headed arrows in fig. 1, 2 and 6-8 are used to illustrate the movement direction of the first movement mechanism, and also correspond to the direction corresponding to the preset eye axis.

Example 1

As will be understood with reference to fig. 1. The embodiment provides a projection device based on cornea reflection, which realizes the function of projecting cornea and can be used for equipment for measuring cornea morphology or observing cornea information. The projection device based on cornea reflection is used for emitting annular light towards the cornea for a plurality of times, and the cornea reflects the annular light for each time one by one; the light reflected by the cornea can be further collected and analyzed to obtain the data of the cornea morphology, and can be amplified and used as an observation object; the components receiving the reflected light 60 are illustrated in dashed boxes in fig. 1 in order to understand the application scenario of a projection device based on corneal reflection.

The projection device based on cornea reflection includes a light source mechanism 10, a plate-like projection disk 20, and a first movement mechanism 30. The projection disk 20 is a light transmissive product. The light source mechanism 10 is located on a first side 201 of the projection disk 20, and in an operating state, the cornea of the object to be detected is located on a second side 202 of the projection disk 20, i.e., the light source mechanism 10 and the cornea are separated on opposite sides of the projection disk 20. The light source mechanism 10 outputs a hollow cone beam 102 with the preset eye axis 40 as an axis at the light output end 101, and projects annular light with the preset eye axis 40 as an axis on the first side 201 of the projection disk 20. As shown in fig. 1, the hollow cone beam 102 is surrounded by light having a uniform thickness, wherein the thickness of the hollow cone beam 102 represents the dimension d of the light in the normal direction of the optical path. The thickness of the hollow cone beam 102 varies, so that the width of the annular light on the projection disk 20 varies. The cornea on the second side 202 of the projection disk 20 receives the annular light to form reflected light 60, and the reflected light 60 can be further reflected after passing through the reflecting portion 203 of the projection disk 20, and the propagation direction is changed so as to be convenient to collect or observe; the reflecting portion 203 is a part of the projection disk 20, and the reflecting portion 203 is located at the center of the annular light and is coaxial with the annular light in terms of the relative position, that is, the reflecting portion 203 is centered on the preset eye axis 40. The first movement mechanism 30 contracts and expands the annular light by adjusting the relative positions of the projection disk 20 and the light output end 101 in the direction of the preset eye axis 40, and the "contracting and expanding" annular light can be understood as that the light source mechanism contracts and expands the radius of the annular light by taking the preset eye axis as the center of a circle, but the width of the annular light is not changed, and the projection device can acquire the reflected light 60 at different positions of the cornea in the process of contracting and expanding the annular light.

Before the cornea of the subject is detected or observed, the light source mechanism 10 is in an on state, the light source mechanism 10 and the projection disk 20 are positioned at the initial position, the subject is positioned at the second side 202 of the projection disk 20, and the subject adapts to the position of the projection disk 20 so that the visual axis thereof coincides with the preset eye axis 40. When the cornea of the tested person is tested, the relative positions of the projection disc 20 and the light output end 101 are adjusted through the first movement mechanism 30, for example, the projection disc 20 and the light output end 101 are gradually close to or gradually far away from each other in the direction of the preset eye axis 40, so that reflected light 60 emitted by the cornea under annular light with different sizes is obtained, and the reflected light 60 can be processed and used independently or can be used after superposition processing.

From the above description, it is clear that the Placido module consisting of the projection device based on corneal reflection and the existing Placido disk and illumination system is used to obtain corneal reflection information by projection onto the surface of the cornea. In contrast, prior art corneal topographers project onto a portion of the surface of the cornea at the same time to obtain incomplete corneal reflection information; the concept of the present disclosure is to obtain complete corneal reflection information based on partial surface projections to the cornea under a plurality of transients, wherein the complete corneal reflection information is formed by superimposing reflection information obtained from the plurality of transients.

More specifically, according to the present disclosure, the projection device based on corneal reflection may be dynamic when in an operating state, where each transient state has one ring light on the projection disc 20, the cornea outputs a set of reflected light 60 correspondingly, multiple sets of reflected light 60 (different transients are generated by the first motion mechanism 30) are generated under multiple transients, and the multiple sets of reflected light 60 can be superimposed to generate corresponding information such as cornea morphology, so that the projection device based on corneal reflection can at least implement the functions of Placido module in the prior art. In particular, in case the respective transient annular lights are set to coincide or overlap with each other in boundary (which is achieved by moving the first movement mechanism, described in detail below), the projection device based on corneal reflection can also acquire reflection information corresponding to the cornea position of the dark ring of the original Placido disc, so that the projection device acquires complete corneal surface morphology information.

The projection device based on corneal reflection has at least the following advantages over the existing Placido module:

(1) Since the projection disk 20 only needs to adopt a light-transmitting plate, such as a frosted glass plate or an acrylic plate, the existing mature product can be directly adopted, the shape of a conical cylinder body does not need to be processed, organic ink does not need to be sprayed to shield light, and the light source mechanism 10 and the first movement mechanism 30 do not need to develop special processing equipment and working procedures for processing, so that the manufacturing precision of the projection device based on cornea reflection is independent of the materials and the production process of the projection disk 20, the first movement mechanism 30 and the light source mechanism 10, and the problem that the manufacturing precision is difficult to improve due to the material and process limitation does not exist. In other words, the projection device based on corneal reflection fulfills the function of the existing Placido module at a lower manufacturing cost.

(2) The annular light projected to the cornea is generated by emitting a hollow cone beam 102 through the light source mechanism 10, only one beam of annular light is arranged on the projection disk 20 under each transient state, the cornea correspondingly outputs a group of reflected light 60, a plurality of groups of reflected light 60 can be obtained by capturing a plurality of transient states, and more comprehensive cornea morphological information can be obtained after the information of each group of reflected light 60 is overlapped; under the condition that the projection disk 20 and the light source mechanism 10 move relatively for the same distance, the number of groups of reflected light 60 obtained by reducing the annular light annular width and the interval time between two adjacent transients is more, and the effect of increasing the number of the annular rings of the conventional Placido disk is the same, namely, the detection precision is improved.

(3) When capturing several transients to obtain multiple sets of reflected light 60, adjusting the relative positions between the projection disk 20 and the light output end 101 can enable the radial dimensions of the annular light under adjacent transients to be partially overlapped or seamlessly connected, so that the reflected light 60 under several transients can obtain information of the whole cornea after being overlapped, and compared with intermittent data output by the existing Placido disk, the data of the projection device based on cornea reflection is continuous and more accurate.

Please understand with reference to fig. 2. In this embodiment, the light source mechanism 10 includes a light source module 103 and a shaping module 104, the light source module 103 is configured to emit parallel light, the shaping module 104 is configured to convert the parallel light into a hollow cone beam 102, and the light output end 101 is located on the shaping module 104. Specifically, the shaping module 104 is disposed between the light source module 103 and the projection disk 20, where the light source module 103 is configured to emit a beam of monochromatic collimated light, such as a visible light beam with a wavelength of 405nm, 532nm, 632.8nm, and the like, and the shaping module 104 receives the monochromatic collimated light and outputs the hollow cone beam 102, and projects the collimated light onto the projection disk 20 as annular light. In this embodiment, the thickness of the same hollow cone beam 102 is the same, and the radial position of the annular light on the projection disk 20 is changed but the annular width is unchanged in the process of adjusting the relative positions of the light output end 101 and the projection disk 20 in the eye axis direction.

In this embodiment, the light source module 103 is adopted to emit a light beam, and the shaping module 104 is utilized to shape the columnar light beam to obtain the hollow cone light beam 102, so that the diameter of the annular light projected onto the projection disk 20 is not dependent on the diameter of the parallel light beam emitted by the light source module 103, but can be realized only by the action of the first movement mechanism 30, and thus the light source module 103 with smaller volume can be adopted to project the annular light with larger diameter onto the projection disk 20.

In this embodiment, the shaping module 104 may include only a single axicon. The parallel light of the light source module is converted into a hollow cone beam 102 by this cone lens. In other embodiments, the shaping module 104 may employ a component or part other than a axicon, so long as it is capable of converting cylindrical monochromatic collimated light into annular light. As shown in fig. 9, which shows further embodiments from the left-hand view of fig. 1, the shaping module 104' alternatively comprises a turntable 71 and a number of axicon lenses 70. Each of the axicon lenses 70 is fixed at a different circumferential position of the turntable 71, and each of the axicon lenses 70 may have a different apex angle. The turntable 71 is rotated so that the axis of any one of the axicon lenses 70 coincides with the preset eye axis 40. When parallel light of the same diameter is input, the taper angles of the hollow cone beams 102 output by different cone lenses are different. The smaller the apex angle of the axicon 70, the larger the cone angle of the hollow cone beam, and the smaller the range of travel of the first movement mechanism 30. In another embodiment, the turntable 71 may be formed as an elongated chassis as shown in fig. 10, and the respective axicon lenses 70 are arranged alternately along the length direction of the chassis (see fig. 1, where the length direction of the chassis is a direction perpendicular to the paper surface). The desired axicon 70 can also be moved to a position aligned with the predetermined eye axis by moving the chassis back and forth.

In this embodiment, the diameter of the parallel light emitted by the light source module 103 is fixed, accordingly, since the shaping module 104 adopts the cone lens, the thickness of the hollow cone beam 102 output by the shaping module 104 is fixed, so that the width of the annular light projected on the projection disk 20 is fixed, that is, the widths of the lights projected to the cornea by the same projection device based on cornea reflection under different transients are consistent, and correspondingly, the difference between the inner diameter and the outer diameter of the annular light under each transient is constant.

In this embodiment, there is a linear motion in the direction of the preset eye axis 40 between the light output end 101 and the projection disk 20, and the linear motion is driven by the first motion mechanism 30, and there may be various specific implementation manners, for example: the first movement mechanism 30 drives the projection disk 20 to move relative to the light source mechanism 10 (as shown in fig. 1), and for example, the first movement mechanism 30 drives the light source module 103 and the shaping module 104 to move together relative to the projection disk 20, or the first movement mechanism 30 drives the shaping module 104 to move relative to the light source module 103 and the projection disk 20.

The radial dimension of the annular light on the projection disk 20 can be changed by displacing the light output end 101 and/or the projection disk 20 in the direction of the preset eye axis 40, in this embodiment, in order to detect or observe the information of each position of the cornea, the cone angle of the hollow cone beam 102 is controlled within 24 ° and the minimum annular light generated on the projection disk 20 has an inner diameter smaller than 4mm, correspondingly, the minimum distance between the light output end 101 and the projection disk 20 in the direction of the preset eye axis 40 is not greater than 9.4mm, and further, the maximum annular light generated on the projection disk 20 has an inner diameter not smaller than 28.8mm, correspondingly, the maximum distance between the light output end 101 and the projection disk 20 in the direction of the preset eye axis 40 is not less than 67.8mm, and in order to achieve the above purpose, the output of the first movement mechanism 30 on the preset eye axis 40 is 58.4mm.

In this embodiment, the first motion mechanism 30 is configured to output stepless linear motion, and can output continuous displacement within a stroke range thereof, and accordingly, the relative distance between the projection disk 20 and the light source mechanism 10 can be adjusted steplessly, so that when capturing reflected light 60 of the cornea in multiple transients, the radial relationship between two adjacent transient corresponding annular lights can be set arbitrarily, and after superposition, the radial relationship can be set locally in a coincident, seamless or spaced manner.

In this embodiment, the first movement mechanism 30 includes a driving module and a detection feedback module, the driving module is used to adjust the relative position of the light source mechanism 10 and/or the projection disk 20 in the direction of the preset eye axis 40, and any of the existing mechanisms capable of outputting linear movement, such as a screw-nut mechanism, a rack-and-pinion mechanism, a linear cam mechanism, a hydraulic cylinder, an air cylinder, and an electric cylinder, may be used. The drive module may be based on any one of electric drive, hydraulic drive and pneumatic drive. When the output end of the driving module is connected with the light source mechanism 10 or the projection disk 20, any one of fixed connection, detachable connection and movable connection can be adopted, so long as at least one of the light source mechanism 10 and the projection disk 20 can be driven to stably move towards the other in the direction of the preset eye axis 40. The driving module can output reciprocating motion along the direction of the preset eye axis 40, and can drive the light source mechanism 10 and the projection disk 20 to be close to each other and drive the light source mechanism and the projection disk to be far away from each other.

The detection feedback module is used for acquiring the relative displacement of the light source mechanism 10 and the projection disk 20; the detection feedback module can obtain the relative displacement by detecting the output quantity of the driving module, and can also obtain the relative displacement by detecting the distance between the light source mechanism 10 and the projection disk 20 and calculating. In this embodiment, the detection feedback module uses a linear grating scale to obtain the relative displacement.

The projection disk 20 only needs to adopt a plate capable of transmitting light, so that the precision requirement is low, the processing cost is low, and the acquisition is easy; the projection disk 20 may be a circular plate, a square plate, or other polygonal plate. The reflecting portion 203 is a part of the projection disk 20, and in this embodiment, the reflecting portion 203 has a solid structure and is integrally formed with other parts of the projection disk 20.

As shown in fig. 1 and 2, in this embodiment, the first surface 204 of the projection disk 20 facing the light source mechanism 10 and the second surface 205 facing away from the projection disk 20 are both planar. In other embodiments, as shown in FIG. 3, the first surface 204 may be spherical with a radius between 100mm and 300mm, or may be ellipsoidal, parabolic, hyperbolic, aspheric, or free-form.

In this embodiment, the first surface 204 and the second surface 205 of the projection disk 20 are frosted surfaces; in other embodiments, it is within the scope of the present invention to alternatively use a frosted surface for one of the first surface 204 and the second surface 205.

In this embodiment, the projection disk 20 is made of glass, and in other embodiments, the projection disk 20 may be made of transparent plastic, such as an acryl plate, as an alternative rear end.

Example 2

The present embodiment provides a projection apparatus based on cornea reflection, which is substantially the same as embodiment 1, except that the thickness d of the light beam output from the light source mechanism 10 of the present embodiment is adjustable.

In this embodiment, the diameter of the parallel light emitted by the light source module 103 is adjustable, correspondingly, as shown in fig. 4, the shaping module 104 adopts a conical lens, and the thickness of the hollow conical light beam 102 output by the shaping module changes along with the change of the diameter of the parallel light, and the two are positively correlated, so that the width of the annular light projected on the projection disk 20 is adjustable, and in the working condition with high precision requirement, the annular light with smaller annular width can be obtained by reducing the diameter of the parallel light emitted by the light source module 103, thereby improving the detection precision. Meanwhile, the projection device based on cornea reflection can be suitable for scenes with large detection precision spans.

Please understand with reference to fig. 5. In this embodiment, the light source module 103 includes a light source 1034 and a lens assembly, the light source 1034 is used for emitting monochromatic collimated light, such as laser light, and the lens assembly is used for adjusting the width of the monochromatic collimated light and emitting the collimated light with the adjusted width to the shaping module 104. Specifically, the lens assembly includes a first lens module 1031, a second lens module 1032, and a third lens module 1033. The first lens module 1031 is configured to receive monochromatic collimated light, the second lens module 1032 is configured to transmit light between the first lens module 1031 and the third lens module 1033, the third lens module 1033 is configured to output parallel light, and the position of the first lens module 1031 and/or the second lens module 1032 and/or the third lens module 1033 in the direction of the preset eye axis 40 is adjustable, so that the diameter of the parallel light output by the third lens module 1033 can be adjusted, fig. 5 is configured to illustrate three transients a, b and c of the light source module 103, wherein two dotted lines are configured to illustrate one movement track of the first lens module 1031 and the second lens module 1032, and the diameter of the output light beam of the third lens module 1033 is changed in three transients a, b and c (c has the smallest diameter and a has the largest diameter). In this embodiment, three lens modules are provided to adjust the diameter of the parallel light beam, and in other embodiments, the number of lens modules may be other integer numbers not less than 2, such as 2, 4 or 5.

In the present embodiment, each of the first lens module 1031, the second lens module 1032 and the third lens module 1033 has one lens, wherein each of the first lens module 1031 and the third lens module 1033 has a convex lens, and the second lens module 1032 has a concave lens. In other embodiments, the first lens module 1031 and/or the second lens module 1032 and/or the third lens module 1033 may alternatively be a plurality of lens assemblies.

In this embodiment, the light source module 103 further includes a second motion mechanism and a third motion mechanism, the second motion mechanism is connected to the first lens module 1031 and is used for driving the first lens module 1031 to move along the direction of the preset eye axis 40, and the third motion mechanism is connected to the second lens module 1032 and is used for driving the second lens module 1032 to move along the direction of the preset eye axis 40. The second movement mechanism and the third movement mechanism may employ existing mechanisms capable of outputting linear movement, for example, any one of a screw nut mechanism, a rack and pinion mechanism, a linear cam mechanism, a hydraulic cylinder, an air cylinder, and an electric cylinder. It should be noted that, in this embodiment, the second movement mechanism and the third movement mechanism may be based on electric driving, hydraulic driving or pneumatic driving, and may also be implemented by manual driving, for example, manually rotating a screw in a screw-nut mechanism, so as to control the linear movement of the first lens module 1031 or the second lens module 1032 connected to the nut.

The present embodiment adjusts the positions of the first lens module 1031 and the second lens module 1032 by using the second movement mechanism and the third movement mechanism, increasing the diameter variation range of the third lens output beam. In other embodiments, as an alternative, only the second movement mechanism or the third movement mechanism may be provided, that is, one position of the single lens assembly may be adjustable, and the other two may be fixedly provided, or the second movement mechanism and the third movement mechanism may be provided, and simultaneously, the fourth movement mechanism may be provided to control the third lens module 1033 to move along the preset eye axis 40, so as to further increase the diameter variation range of the output beam of the third lens.

In this embodiment, the light source module 103 adopts the above structure to emit the light beam with adjustable diameter, and in other embodiments, as an alternative means, the light source module 103 may directly use the existing continuous variable magnification beam expander.

Other parts of the projection device based on cornea reflection in this embodiment are the same as those in embodiment 1, and will not be described here again.

Example 3

With continued reference to fig. 1, this embodiment provides a cornea camera, which employs the projection apparatus based on cornea reflection provided in any of the above embodiments, and further includes an observation module having an incident end and an observation end, the reflected light 60 passing through the reflection portion 203 and then entering the incident end, the incident end further reflecting the reflected light 60 toward the observation end along a preset direction, and the observation end is used for observing the reflected light 60. In this embodiment, the preset direction is perpendicular to the direction in which the preset eye axis 40 is located, and in other embodiments, the preset direction and the preset eye axis 40 may be inclined, so that the reflected light 60 passing through the reflecting portion 203 does not interfere with the light source mechanism 10. When the projection device based on corneal reflection shown in fig. 1 is applied in this embodiment, the dashed box represents the observation module.

In this embodiment, the observation module changes the direction of the reflected light 60 and plays a role of amplifying, specifically, the observation module includes a beam splitter component and an amplifying mirror module, the incident beam splitter component is used to change the propagation direction of the reflected light 60, and the reflected light 60 is sequentially reflected by the beam splitter component and amplified by the amplifying mirror module, so as to be observed more clearly.

In the application process, the first movement mechanism can be enabled to be not operated, cornea information can be observed in a static mode, and the first movement mechanism can be enabled to be in electrodeless movement, so that morphological information of different positions of the cornea can be observed in a dynamic mode.

The morphological information of the local position of the cornea of the film camera is amplified, in this embodiment, the amplified information can be directly observed from the observation end, and in other embodiments, other devices may be further installed at the observation end, so as to further collect and/or analyze the amplified information.

Example 4

Please understand with reference to fig. 6. The present embodiment provides a corneal topography instrument for detecting a corneal topography. The corneal topographer includes the corneal reflection-based projection device provided in any of the embodiments above, and further includes an imaging module 50, the imaging module 50 for receiving the reflected light 60 and generating image information. The cornea topographic map further comprises an image processing module, the imaging module 50 transmits image information to the image processing module, and recording, analyzing and calculating the image information are realized by the image processing module; in specific implementation, the image processing module can be realized through an upper computer.

In this embodiment, the imaging module 50 has a first end 501 and a second end 502, wherein the first end 501 is configured as a beam splitter structure for receiving the reflected light 60 reflected by the cornea and transmitting the reflected light 60 to the second end 502, and the first end 501 to the second end 502 are arranged along a direction perpendicular to the preset eye axis 40. In this embodiment, the first end 501 of the beam splitter does not affect the projection of the hollow cone beam 102 to the projection disk 20, and the arrangement of the imaging module 50 along the direction perpendicular to the preset eye axis 40 reduces the space occupied by the imaging module 50 around the preset eye axis 40, and reduces the risk that the hollow cone beam 102 is blocked by the portion other than the first end 501 of the imaging module 50. In other embodiments, the first end 501 to the second end 502 may be arranged in a direction oblique to the preset eye axis 40 as an alternative.

In this embodiment, the imaging module 50 includes a beam splitter element 503, an imaging lens assembly 504 and an image sensor 505, the reflected light 60 is reflected into the imaging lens assembly 504 by the beam splitter element 503, the imaging lens assembly 504 focuses the light on the image sensor 505, the image sensor 505 is used for converting the light signal into an electrical signal, the electrical signal is processed to generate image information, and the image information is transmitted to the image processing module. The first end 501 includes a spectroscopic element 503 and the second end 502 includes an image sensor 505.

In this embodiment, the beam splitter element 503 adopts a filter (more specifically, a transflective filter) that is disposed at an angle of 45 ° with respect to the predetermined eye axis 40, so as to transmit the reflected light 60 from the cornea to the imaging lens group 504 along a direction perpendicular to the predetermined eye axis 40. The means for mounting the beam splitter element 503 may be made of a light transmissive material to prevent obstruction of the hollow cone beam 102. Since the imaging lens group 504 focuses the reflected light 60 to the image sensor 505, the positional relationship between the imaging lens group 504 and the image sensor 505 is related to the position of the cornea, which is fixed by default, and in this embodiment, the imaging module 50 has no displacement output in the direction of the preset eye axis 40, so that the imaging lens group 504 and the image sensor 505 are relatively stationary, and in other embodiments, if the imaging module 50 moves relatively to the cornea in the direction of the preset eye axis 40, the imaging lens group 504 and the image sensor 505 need to move relatively in the direction perpendicular to the preset eye axis 40. The imaging lens group 504 may be any one of a lens group formed by a single lens, a double cemented lens, an aspherical lens and any combination thereof, the image sensor may be a CCD or CMOS, and the imaging lens group 504 and the image sensor 505 may be implemented by using the prior art, which will not be described in detail.

As shown in fig. 6, in the present embodiment, the first movement mechanism 30 is connected to the projection disk 20, and is used for driving the projection disk 20 to move in the direction of the preset eye axis 40, and the light source mechanism 10, the imaging module 50 and the image processing module are fixedly arranged. Specifically, the output end of the first movement mechanism 30 is connected to the projection disk 20, and the two can be fixed by clamping, fastening, welding or other methods, so as to maintain the stability of the projection disk 20 during movement. In use, the light source mechanism 10 and the imaging module 50 are stationary, the first motion mechanism 30 is dynamic, and the projection disk 20 is driven to move relative to the light source mechanism 10 from far to near or from near to far by controlling the motion of the first motion mechanism 30, and during this time the imaging module 50 is controlled to image a number of transients.

The corneal topographer also includes a mounting enclosure (not shown) that encloses a mounting cavity in which the corneal reflection-based projection device and imaging module 50 are built. The mounting cover plays an integrated role in integrating the light source mechanism 10, the projection disk 20, the first movement mechanism 30 and the imaging module 50; the mounting cover also provides dust protection and prevents mechanical damage to the projection device and imaging module 50 from the external environment. The mounting cover is provided with a detection hole corresponding to the projection disk 20 in a direction to facilitate smooth propagation between the cornea outside the mounting cover and the projection disk 20 inside the mounting cover. In use, the eye is aligned with the detection aperture, annular light is incident on the cornea of the eye through the detection aperture, and reflected light 60 generated by the cornea is incident on the projection disk 20 after passing through the detection aperture.

The function and principle of the corneal topographer will be described in connection with its structure. The cornea topography instrument projects cornea, then obtains image information according to light information reflected by cornea, the image information can be used independently to represent local form information of cornea, and can also be used in a superposition way, after superposition, the form of cornea can be reflected more comprehensively, and even the real form of cornea can be reflected completely. The method comprises the steps that information obtained after superposition of image information is defined as a first result, the embodiment form of the first result is consistent with the embodiment form of information obtained by projecting cornea through an existing Placido module and imaging reflected light through a photographing system, but the precision of the first result can be flexibly adjusted by adjusting the interval between adjacent annular lights, and the precision of the first result can be improved by reducing the width of the annular lights under the condition that the width of the annular lights is adjustable, so that the cornea topographic map instrument of the embodiment can be applied to scenes with different precision requirements and working conditions requiring precision adjustment; in addition, the width of the annular light can be adjusted by controlling the diameter of the output beam of the light source module 103 and/or adjusting the cone angle of the hollow cone beam 102, the interval between adjacent annular lights can be adjusted by adjusting the output quantity of the first motion mechanism 30 and/or the shooting frequency of the imaging module 50, and the operation of adjusting the detection precision of the cornea topographic map instrument is simple and convenient, and the adjustment cost is low.

Taking the image information superposition as an example to further describe the working principle of the cornea topographic map instrument, in the process of the relative motion of the projection disk 20 and the light source mechanism 10, the imaging module 50 grabs a plurality of moments to image, and the adjacent two moments correspond to annular light superposition to possibly generate any one of three conditions of local superposition, seamless connection and existence interval, and when a plurality of image information are superposed, if noise occurs due to the local superposition of the annular light, one group of data in the superposition area can be removed. For a scene with intervals, provided that the radial interval between annular lights is the same as the radial interval between dark rings of the existing Placido disk, the detection effect of the cornea topographer is the same as that of the annular lights, but the cornea topographer is simple in structure and simple in manufacturing process.

Continuing to describe the working principle of the cornea topography instrument by taking the image information superposition as an example, setting different parameters can obtain different detection precision, for example, adjusting the initial distance between the light output end 101 and the projection disk 20 and/or adjusting the relative movement speed between the light output end 101 and the projection disk 20 and/or adjusting the shooting frequency of the imaging module 50, and can control the position relationship between the annular light corresponding to the n+1th shooting and the annular light corresponding to the n-th shooting of the imaging module 50, so as to obtain different detection precision. In the practical application process, a chip is set to control the first motion mechanism 30, the imaging module 50 and the light source mechanism 10, different modes can be written in the chip in advance, the detection precision corresponding to each mode is different, the operation parameter information of the first motion mechanism 30, the imaging module 50 and the light source mechanism 10 is preset in each mode, each mode corresponds to a key, and after the user selects the key with the required precision according to the detection requirement, the chip controls the first motion mechanism 30 and/or the imaging module 50 and/or the light source mechanism 10 to act according to the preset parameter information.

Continuing to describe the working principle of the cornea topography instrument by taking the use of overlapping of image information as an example, when the imaging module 50 performs imaging at equal intervals, the annular light corresponding to each image information is uniformly distributed, namely the widths of overlapping any two annular lights are consistent after overlapping, or the widths of the intervals of overlapping any two annular lights are consistent, or the overlapping of any two annular lights is not consistent and is gapless.

Example 5

The present embodiment provides a corneal topographer, which is different from embodiment 4 in that the object driven by the first movement mechanism 30 is specifically as follows:

as shown in fig. 7, in the present embodiment, the first movement mechanism 30 is configured to drive the shaping module 104 to move relative to the projection disk 20, where an output end of the first movement mechanism 30 is connected to the shaping module 104 to drive the shaping module to move along the preset eye axis 40, and the first movement mechanism and the shaping module can be fixed by clamping, fastening, welding, or other manners to maintain stability of the shaping module 104 during movement. Imaging module 50 is configured to be relatively stationary with respect to projection disk 20 while imaging module 50, projection disk 20 and the cornea are relatively stationary during use, and accordingly, the relative positions of imaging lens assembly 504 and image sensor 505 are unchanged. The imaging module 50 is secured to the mounting cup by clamping, fastening, welding, etc. the projection plate 20.

In this embodiment, the light source module 103 is disposed to be relatively stationary with the projection disk 20, and the light source module 103 is fixed on the mounting cover by clamping, fastening, welding, etc., and as an alternative, it is also within the scope of the present invention that the light source module 103 is disposed to be relatively stationary with the shaping module 104.

In order to obtain a more complete and precise cornea shape, the smaller the minimum annular light inner diameter of the shaping module 104 projected on the projection disk 20 is, the better, so in this embodiment, a through hole 5031 for the shaping module 104 to pass through is provided on the spectroscope element 503, and when the first movement mechanism 30 drives the shaping module 104 to move, the shaping module 104 can partially or entirely pass through the through hole 5031 to project the annular light with the smaller inner diameter on the projection disk, so as to obtain a more complete and precise cornea shape. The size of the through hole 5031 is sufficient as long as the above function is satisfied, and the aperture of the through hole 5031 is set within 4mm in this embodiment.

In use, the projection disk 20 and the imaging module 50 are stationary, and the shaping module 104 is driven by the first movement mechanism 30 to move from far to near or from near to far relative to the projection disk 20, during which the imaging module 50 performs imaging.

It should be noted that, the relative sizes of the shaping module 104 and the light source module 103 illustrated in fig. 1 and fig. 7 are different, but are not contradictory, and fig. 1 and fig. 7 are used for illustration so as to facilitate understanding of the present invention in conjunction with text information, and the sizes of the various parts in the figures do not represent the sizes in practical use, and even for the same component, the sizes may also be different if the models selected in practical use are different.

Other parts of the corneal topographer in this embodiment are the same as those in embodiment 4, and will not be described in detail here.

Example 6

The present embodiment provides a corneal topographer, which is different from embodiment 4 in terms of the object driven by the first movement mechanism 30 and the structural change caused by the difference in the driving object, specifically, as follows:

as shown in fig. 8, the output end of the first movement mechanism 30 is connected to the shaping module 104 and the imaging module 50, and is used for driving the shaping module 104 and the imaging module 50 to move together in the preset eye axis 40 direction relative to the projection disk 20. While an imaging lens group 504 within the imaging module 50 is arranged to move between the spectroscopic element 503 and the image sensor 505 to focus light on the image sensor 505. In this embodiment, the light source module 103 is disposed at a relatively stationary position with respect to the shaping module 104, and alternatively, the light source module 103 may be disposed at a relatively stationary position with respect to the projection disk 20.

In this embodiment, the imaging module 50 further includes a fifth movement mechanism, an output end of the fifth movement mechanism is connected to the imaging lens group 504, and is used to drive the imaging lens group 504 to reciprocate between the beam splitter element 503 and the image sensor 505, so as to focus light on the image sensor 505; the solid double arrow lines in fig. 8 are provided above and below to illustrate that the imaging lens group 504 is not dynamic during use. The fifth movement mechanism may employ an existing mechanism capable of outputting linear movement, for example, any one of a stepping motor, a screw nut mechanism, a linear cam mechanism, a rack and pinion mechanism, a hydraulic cylinder, an air cylinder, and an electric cylinder. The fifth movement mechanism and the first movement mechanism 30 may be provided in a linked manner, and the fifth movement mechanism automatically operates according to the output of the first movement mechanism 30.

In use, the projection disk 20 is in a static state, the shaping module 104 and the imaging module 50 are driven to move together towards a direction approaching or separating from the projection disk 20 by the first movement mechanism 30, and the imaging lens set 504 is driven to move by the fifth movement mechanism, so that light is always focused on the image sensor 505, and meanwhile, the imaging module 50 is controlled to perform imaging.

Compared with the prior art, the beneficial effect of this application scheme lies in:

(1) Because the projection disc only needs to adopt the light-transmitting plate, such as a frosted glass plate, the existing mature product can be directly adopted, the shape of the conical cylinder body does not need to be processed, organic ink does not need to be sprayed to shield light, and the light source mechanism and the first movement mechanism do not need to develop special processing equipment and working procedures for processing, so that the manufacturing precision of the projection device based on cornea reflection does not depend on the materials and the production process of the projection disc, the first movement mechanism and the light source mechanism, and the problem that the manufacturing precision is difficult to improve due to the limitation of the materials and the process does not exist.

(2) The annular light projected to the cornea is generated by emitting a hollow cone beam through a light source mechanism, only one beam of annular light is arranged on a projection disc under each transient state, the cornea correspondingly outputs a group of reflected light, a plurality of groups of reflected light can be obtained by capturing a plurality of transient states, and comprehensive and accurate cornea form information can be obtained after the information of each group of reflected light is overlapped; under the condition that the relative movement of the projection disk and the light source mechanism is the same for a certain distance, the ring width of the annular light is reduced, the interval duration between two adjacent transients is reduced, the number of groups of reflected light is more, the effect of increasing the number of rings of the conventional Placido disk is the same, namely, the detection precision is improved, but the ring width of the annular light is reduced, the interval duration between the two adjacent transients is reduced without complex technology, and the implementation is easy.

(3) When capturing a plurality of transients to obtain a plurality of groups of reflected light, the relative positions between the projection disk and the light output end are adjusted, so that the radial sizes of the annular light in adjacent transients are partially overlapped or seamlessly connected, the information of the whole cornea can be obtained after the reflected light in a plurality of transients is overlapped, and compared with intermittent data output by the conventional Placido disk, the data of the projection device based on cornea reflection are continuous and more accurate.

The method for generating a corneal topography is described next.

Fig. 10 illustrates a schematic diagram of an example environment 1000, according to an embodiment of the disclosure. As shown in fig. 10, the example environment 1000 includes a computing device 1010, a plurality of first back-lit images 1020, a plurality of second back-lit images 1030, and a corneal topography map 1040.

Computing device 1010 may include, but is not limited to, a corneal topographer (e.g., the corneal topographer above), an ophthalmic medical device, a personal computer, a personal digital assistant, a wearable device, a tablet computer, a smart phone, and the like. In some embodiments, the computing device 1010 may have or be coupled to an image acquisition apparatus for acquiring cornea images.

The computing device 1010 may be used to obtain a plurality of first back-light-circle images 1020 for the same cornea, the plurality of first back-light-circle images acquired by an axial stepper motor moving the image acquisition apparatus at a plurality of positions in a preset eye axis direction; determining the number of pixels occupied by the width of the backlight loop in each first backlight loop image; fitting the determined number of pixels to a parabola with an upward opening; determining the position of an axial stepping motor corresponding to the lowest point of the parabola; after the axial stepping motor is controlled to move from a preset zero position to the determined position of the axial stepping motor, a plurality of second backlight loop images 1030 of the target cornea are acquired, and the plurality of second backlight loop images have diaphragms with different diameters; and generating a corneal topography 1040 based on the plurality of second back-light ring images 1030.

Thus, the moving focusing time for the cornea can be greatly shortened.

Fig. 11 shows a schematic diagram of an example of a method 1100 for generating a corneal topography, according to an embodiment of the disclosure. In fig. 11, various actions may be performed, for example, by the computing device shown in fig. 10. It should be appreciated that method 1100 may also include additional acts not shown and/or may omit acts shown, the scope of the present disclosure being not limited in this respect.

At block 1102, the computing device 1010 acquires a plurality of first back-light images 1020 for the same cornea, the plurality of first back-light images acquired by an axial stepper motor moving a plurality of positions of an image acquisition apparatus in a preset eye axis direction.

An image acquisition device such as the corneal topographer above. The corneal topographer may be fitted with an axial stepper motor and guide rail, for example. The axial stepping motor can control the main body of the cornea topography instrument to move along the guide rail in the preset eye axis direction, so that a plurality of back aperture images aiming at the same cornea are acquired at a plurality of positions in the preset eye axis direction. Specifically, the axial stepper motor may control the movement of the corneal topographer as a whole in the direction of the preset eye axis, so that the light output end 101 of the corneal topographer outputs light beams to the cornea at different distances from the cornea, thereby realizing acquisition of a plurality of back aperture images for the same cornea.

At block 1104, the computing device 1010 determines a number of pixels occupied by a backlight collar width in each first backlight collar image.

Binarization processing may be performed on each of the first backlight collar images to generate a binary image. After the binarization process, a line segment (the ray passes through the center coordinate of the aperture) can be made at the peripheral aperture position to cover the whole width, and the number of pixels (only the aperture or the light ring) with the gray value of 255 on the line segment, namely the number of pixels occupied by the back aperture width, is calculated.

At block 1106, the computing device 1010 fits the determined number of pixels to a parabola with an opening up.

At block 1108, the computing device 1010 determines an axial stepper motor position corresponding to the lowest point of the parabola.

By calculating the width (i.e. the number of pixels) of the peripheral single ring aperture, the condition of focusing of the image can be judged, and the larger the width is, the smaller the defocusing is, so that the axial stepping motor position corresponding to the lowest point of the parabola is the optimal focusing position of the cornea topography instrument for the cornea, and the focus of the light beam output by the light output end 101 of the cornea topography instrument can fall on the cornea on the second side of the projection disc.

At block 1110, the computing device 1010 controls the axial stepper motor to move from a preset null to the determined axial stepper motor position and then acquires a plurality of second back-light images 1030 of the target cornea, the plurality of second back-light images having apertures of different diameters.

After the axial stepper motor is controlled to move from a preset zero position to a determined axial stepper motor position, an image acquisition device such as the corneal topographer is positioned at an optimal focusing position, so that automatic quick moving focusing is realized. Acquiring a plurality of second back-light loop images of the target cornea may be accomplished using the corneal topographer above, wherein the corneal topographer comprises a corneal reflection-based projection device and an imaging module.

The projection device based on cornea reflection comprises a light source mechanism, a platy projection disk and a first movement mechanism, wherein the light source mechanism is provided with a light output end, the light source mechanism is used for outputting a hollow cone beam taking a preset eye axis as an axis at the light output end and projecting annular light on a first side of the projection disk, and the first movement mechanism contracts and expands the annular light by adjusting the relative position between the light output end and the projection disk in the preset eye axis direction; the cornea on the second side of the projection disk receives the annular light to form reflected light, and the reflected light can be changed in light path after passing through the reflecting part of the projection disk; the reflector is located in the center of the annular light and is coaxial with the annular light.

The imaging module is used for receiving the reflected light and generating image information. The imaging module comprises a spectroscope element, an imaging lens group and an image sensor, reflected light is reflected into the imaging lens group through the spectroscope element, and the imaging lens group focuses light on the image sensor.

The method comprises the steps of collecting a plurality of second backlight loop images of a target cornea, wherein the step of controlling the first movement mechanism to drive the light output end of the light source component and the projection disc to move relatively for a first distance in the direction of a preset eye axis, and the step of controlling the imaging module to shoot the cornea positioned on the second side of the projection disc and obtain the plurality of second backlight loop images. In particular, a region of interest for a placido disc aperture may be acquired, and an imaging module may be controlled to take a photograph of a cornea located on a second side of the projection disc and obtain a plurality of second back-illuminated images such that apertures of different diameters are located within the region of interest.

Taking the central point position (equivalent to the image central point) of a shooting interface of the cornea topography instrument as a preset central point (X0, Y0), wherein the distance between the acquired image cornea central point, namely the center (Xn, yn), and the preset central point is not more than 35 pixels, namely [ (X0-Xn)/(2+ (Y0-Yn)/(2 ]/(1/2 < = 35 pixels). The offset of the center point of the cornea within this range does not cause the useful area of the back aperture to move out of the area of interest.

Through stable sampling in the region of interest, the execution rate of the method can be effectively improved, and the influence of factors such as image offset jitter and the like caused by objective reasons in the sampling process is eliminated.

In one embodiment, the method of photographing may use any of the corneal topographers described above to photograph the cornea located on the second side 202 of the projection disk 20, the method comprising the steps of:

the first movement mechanism 30 is controlled to drive the light output end 101 and the projection disk 20 to relatively move a first distance in the direction of the preset eye axis 40, and the imaging module 50 is controlled to shoot and obtain a plurality of second backlight ring images during the period, so that diaphragms with different diameters are located in the region of interest.

In this embodiment, the axis of the cornea located on the second side 202 coincides with the preset axis before the acquisition, that is, the cornea is located, and the specific locating mode may be to adapt to the position of the projection disk 20 by moving the face of the person, or may be to set a locating portion on the mounting cover, to initially locate the face by using the locating portion, and then fine-tune the face based on the locating portion to adapt to the position of the projection disk 20.

In this embodiment, in the step of controlling the first movement mechanism 30 to drive the light output end 101 and the projection disk 20 to move relatively by a first distance along the preset eye axis 40, the imaging module 50 is controlled to capture and obtain a plurality of second back light images:

The first motion mechanism 30 is configured to output an electrodeless motion (forward and backward rectilinear motion along a preset eye axis), and control the first motion mechanism 30 to drive the projection disk 20 to move at a uniform speed for a first distance relative to the light output end 101, where the imaging module 50 shoots at a preset frequency, so that annular lights corresponding to each image information are uniformly distributed after being superimposed; the initial distance between the light output end 101 and the projection disk 20 and/or the relative movement speed between the light output end 101 and the projection disk 20 and/or the shooting frequency of the imaging module 50 are/is adjusted so that the outer diameter of the annular light corresponding to the (n+1) th shooting of the imaging module 50 is equal to the inner diameter of the annular light corresponding to the (n) th shooting, and thus the first result is continuous and non-overlapping. Indeed, in other methods, the outer diameter of the annular light corresponding to the n+1th shot of the imaging module 50 may be larger than the inner diameter of the annular light corresponding to the n-th shot.

Alternatively or additionally, in the step of controlling the first movement mechanism 30 to drive the light output end 101 and the projection disk 20 to relatively move a first distance in the direction of the preset eye axis 40, the imaging module 50 is controlled to shoot and obtain a plurality of second backlight images:

the first motion mechanism 30 is used for outputting an electrodeless motion, the first motion mechanism 30 drives the projection disk 20 and the light output end 101 to relatively move for a plurality of times to reach a relative motion amount of a first distance, and the imaging module 50 is controlled to shoot at a gap between the two relative motions to form graphic information. The amount of movement of each relative movement of the projection disk 20 and the light output end 101 is the same, the initial distance between the light output end 101 and the projection disk 20 is adjusted, and/or the relative movement speed between the light output end 101 and the projection disk 20 is adjusted, and/or the shooting frequency of the imaging module 50 is adjusted, so that the outer diameter of the annular light corresponding to the (n+1) th shooting of the imaging module 50 is equal to the inner diameter of the annular light corresponding to the (n) th shooting, and the first result is continuous and non-overlapping. Indeed, in other methods, the outer diameter of the annular light corresponding to the n+1th shot of the imaging module 50 may be larger than the inner diameter of the annular light corresponding to the n-th shot.

Therefore, when a plurality of transients are captured to obtain a plurality of groups of reflected light, the relative positions between the projection disc and the light output end are adjusted, and the radial sizes of the annular light in adjacent transients can be partially overlapped or seamlessly connected, so that the information of the whole cornea can be obtained after the reflected light in a plurality of transients is overlapped, and compared with the intermittent data output by the conventional Placido disc, the data of the projection device based on cornea reflection is continuous and more accurate.

Returning to fig. 11, at block 1112, computing device 1010 generates a corneal topography map 1040 based on the plurality of second back-light ring images 1030.

Therefore, the optimal focusing position corresponding to the lowest point can be determined by counting the number of pixels occupied by the widths of the backlight rings of a plurality of backlight ring images shot by the image acquisition device at a plurality of positions in the preset eye axis direction and fitting the number of pixels into a parabola with an upward opening, so that automatic moving focusing is realized, the moving focusing time for cornea can be greatly shortened, and a cornea topographic map can be generated more quickly and accurately.

An eye image including the target cornea may also be acquired prior to acquiring the plurality of second back-porch images of the target cornea.

A lateral pixel offset and a longitudinal pixel offset between a pupil center point in the eye image and a center point of an interface of the image capture device are determined.

Specifically, the eye region may be positioned first, the approximate extent of both eyes may be marked by the rectangles, the pupil center position may be determined by pupil identification within the rectangles, and the pupil center point may be marked by a cross. The method can be realized by haar-like feature recognition and cascading adaboost classifiers. Speed boost aspect: the integral image is utilized to extract the image characteristic value, so that the speed is high. Meanwhile, the most useful features are reserved by utilizing the feature screening characteristics of the adaboost classifier, so that the operation complexity in detection is reduced. Accuracy improvement: the adaboost classifier is modified to become a cascade adaboost classifier, so that the accuracy of face detection is improved (the omission ratio and the false detection ratio are reduced).

The center coordinates may then be determined at the center of the interface of the image acquisition device based on the original pixel value parameters thereof.

Next, the lateral pixel shift and the longitudinal pixel shift can be determined using the pupil center position and the center coordinates.

After determining the lateral pixel shift and the longitudinal pixel shift, the number of lateral movement steps of the lateral stepper motor of the image acquisition device and the number of longitudinal movement steps of the longitudinal stepper motor of the image acquisition device may be determined based on a predetermined relationship between the lateral movement distance of the image acquisition device and the pixel movement distance of the imaging point in the interface, the lateral pixel shift, and the longitudinal pixel shift.

For example, the relationship between the stepper motor and the actual image pixels may be determined: the step motor in X, Y direction needs m steps to move one circle, and the movement distance of the image in the corresponding camera interface is a and b (mm) respectively. According to the actual size and resolution 2056X 1542pixels of the CCD panel, the ratio of the actual spatial movement distance in the X and Y directions to the pixel movement distance of the imaging point on the camera is Xp and Yp, respectively, and the number of movement steps Xstep and Ystep required by the X, Y-direction stepping motor is as follows.

Where dx denotes the lateral pixel offset and dy denotes the longitudinal pixel offset.

After determining the lateral movement step number and the longitudinal movement step number, the lateral stepping motor may be controlled to move the lateral movement step number and the longitudinal stepping motor may be controlled to move the longitudinal movement step number.

Therefore, the alignment of the centers of human eyes can be realized, and the accuracy of the acquired backlight ring image and the generated cornea topographic map is improved.

Fig. 12 shows a schematic diagram of an example of a method 1200 for generating a corneal topography, in accordance with an embodiment of the disclosure. In fig. 12, various actions may be performed, for example, by the computing device shown in fig. 10. It should be appreciated that method 1200 may also include additional acts not shown and/or may omit acts shown, the scope of the present disclosure being not limited in this respect.

At block 1202, the computing device 1010 performs offset correction on the plurality of second backlight loop images to obtain an offset corrected plurality of second backlight loop images.

The computing device 1010 may perform the following steps for each of the plurality of second back-lit images to determine the pupil center.

First, computing device 1010 may perform a circle detection within a region of interest.

In particular, the computing device 1010 may smooth filter the second backlight collar image to generate a smooth filtered second backlight collar image. For example, gaussian smoothing filtering may be used, and the filtering effect best matches the actual corneal radius of curvature calculation when the convolution size is set to 5*5, for example. The original image is convolved to reduce redundant content of the image, reduce variability of human eyes (such as various incidental objects, concave-convex of skin and the like), and facilitate subsequent circular detection. The computing device 1010 may binarize the smoothed filtered second backlight collar image to generate a binarized second backlight collar image. The computing device 1010 may determine an area for circle detection in the binarized second backlight collar image based on the pre-acquired maximum pixel count range and minimum pixel count range; and performing circular detection in the determined area for circular detection and fitting based on the preset sensitivity value.

The circle detection may be implemented using a hough transform. In hough transform, a scalar setting of radius can be performed on a circular object to be detected, and the number of occupied pixels can be used as a specified digital type scalar calculation; it is also possible to set a range of radii with two element vectors of integers of the specified numerical type as the maximum value rmax, minimum value rmin of the range. After the radius range of the circle to be detected is determined in a targeted manner, the characteristic polarity of the circular object to be detected can also be set, and the value in the image, namely 0 or 1, can be replaced by Dark ' or ' Bright ' because of the binary image, and the characteristic polarity of the object to be detected can be detected by ' Bright ' because the back aperture of the object to be detected is Bright compared with the background. In addition, the calculation method may be set as a phase encoding method. The sensitivity factor plays a great role in the process of detecting the circle by the Hough transform, and the range of the sensitivity factor can be set between 0 and 1.

If a circle is detected within the region of interest, computing device 1010 may take the center of the detected circle as the pupil center.

If a circle is not detected within the region of interest, the computing device 1010 may perform an elliptical detection within the region of interest to determine an elliptical center of the corresponding aperture as the pupil center.

Subsequently, the computing device aligns a plurality of pupil centers corresponding to the plurality of second back-up light ring images to a preset center to obtain a plurality of offset corrected second back-up light ring images.

For example, a center offset of the pupil center (Xn, yn) with respect to the camera center point (X0, Y0) may be calculated: X0-Xn, Y0-Yn. The method comprises the following specific steps: after the size of the matrix in the XY direction of the original image obtained by shooting is obtained (namely, the size of the pixel value of the size of the whole camera interface), the center coordinate of the matrix of the original image (namely, the center point coordinate (X0, Y0) of the camera interface) can be expressed; pupil center coordinates (Xn, yn) obtained by the above steps, from which the center point offset is calculated: X0-Xn, Y0-Yn.

Shifting the images X0-Xn in the X direction and Y0-Yn in the Y direction by a translation function algorithm, overlapping the centers of the pupils with the original centers, and restoring the image, wherein the positive and negative of the displacement are determined by the offset direction, and the calculation result is signed.

Thus, offset correction of the image is realized, and a placido disc aperture image is conveniently and accurately generated.

At block 1204, the computing device 1010 superimposes the offset corrected plurality of second backlight ring images to generate a placido disk aperture image.

For example, the center point of each image is used as a reference point to perform the image superposition process, wherein the important parameters to be considered are to ensure that the display intensity of each image subjected to superposition processing is the same, so as to ensure that the brightness of all final light rings is the same, and the superimposed image is a complete and continuous scanned placido disc light ring image.

At block 1206, computing device 1010 generates a corneal topography map based on the placido disc aperture image.

Therefore, the method can support continuous imaging of the aperture on the cornea of the human eye in an electrodeless scanning mode to realize uninterrupted cornea aperture image acquisition, offset correction and superposition are carried out on the acquired images, and the generated placido disc aperture image is more continuous and accurate, so that the integrity and the precision of the generated cornea topographic map are greatly improved.

Fig. 13 shows a schematic diagram of an example of a method 1300 for acquiring a region of interest for a placido disc aperture according to an embodiment of the disclosure. In fig. 13, various actions may be performed, for example, by the computing device shown in fig. 10. It should be appreciated that method 1300 may also include additional acts not shown and/or may omit acts shown, the scope of the present disclosure being not limited in this respect.

At block 1302, the computing device 1010 obtains a plurality of third back-lit images for the same cornea, the plurality of third back-lit images including apertures of different diameters.

At block 1304, the computing device 1010 determines a plurality of diameter pixel numbers for a plurality of apertures.

In particular, the computing device 1010 may perform the following steps for each of the plurality of third backlight collar images to determine the number of diameter pixels.

First, the computing device 1010 may binarize the third backlight collar image to generate a binary image. The binary image, i.e. the gray value has only two values of 0 and 255.

The computing device 1010 may then detect connected circular regions in the binary image. Any suitable connected domain detection algorithm may be employed.

Subsequently, the computing device 1010 may fill the connected circular region with predetermined pixel values. For example, the predetermined pixel value may be 255, that is, only 255 for the gray value inside the filled connected circular area.

Finally, the computing device 1010 may determine a number of pixels having a predetermined pixel value across the diameter of the filled connected circular area as a diameter pixel number of the aperture. For example, the number of pixels of the diameter can be obtained by drawing a line segment which communicates with the center of the circle in the circular region and traversing the diameter, and counting the number of pixels of the diameter by calculating the number of gray values of 255.

At block 1306, the computing device 1010 determines a maximum diameter pixel number of the plurality of diameter pixel numbers. For example, the number of diameter pixels of the maximum aperture can be about 730 pixels.

At block 1308, the computing device 1010 determines a region of interest for the placido disk aperture based on the maximum diameter pixel number and the preset offset.

The preset offset includes, for example, but is not limited to, 35 pixels. The region of interest may be determined, for example, as a square with a side length of a preset offset of maximum diameter pixel number +2. Taking the maximum diameter pixel number of 730 and the preset offset of 35 as an example, the region of interest may be a square of 800×800. That is, a circular range of 35 pixels with a surrounding radius is reserved by taking the center point of the camera as the center of the circle, and the allowable movement range of the center point of the pupil of the human eye is within the circle. All apertures can be identified within this region of interest.

Therefore, the interested area for the plaicido disk aperture can be determined, stable sampling is convenient for the aperture, and efficiency is improved.

Fig. 14 shows a schematic diagram of an example of a method 1400 for elliptical detection within a region of interest according to an embodiment of the disclosure. In fig. 14, various actions may be performed, for example, by the computing device shown in fig. 10. It should be appreciated that method 1400 may also include additional acts not shown and/or may omit acts shown, the scope of the present disclosure being not limited in this respect.

At block 1402, the computing device 1010 performs boundary detection within the region of interest resulting in a boundary map.

The boundary detection may include the following steps:

carrying out gray level transformation on the region of interest to obtain a gray level image: the usual method of graying is based on the brightness equation that the RGB components are weighted-averaged by different coefficients, depending on the sensitivity of the human eye to different colors.

f(i，j)＝0.3R(i,j)+0.59G(i,j)+0.11B(i,j)。

And denoising the gray level image to obtain a denoising image. Noise reduction can be performed, for example, by convolving the gray-scale image with the gaussian template used (specified standard deviation).

The direction of the brightness gradient of each pixel in the noise reduction image is determined. For example, each pixel point on the noise reduction image can be traversed from the horizontal, vertical, main diagonal and auxiliary diagonal directions, and all points in the noise reduction image centered on the point and within the template as a window are convolved with the template, so that the brightness gradient map and the brightness gradient directions of each point are obtained from the noise reduction image.

Non-maximum suppression is performed on pixels in the noise reduced image based on the luminance gradient direction. In order to obtain the candidate edges of the single pixels, the area where the non-zero pixel points are located is thinned. The method comprises the following specific steps: for one point P (x, y), the intersection points (x 1, y 1) and (x 2, y 2) of the P point gradient direction and the square formed by the 8-connected neighborhood points are calculated. The coordinates of the intersection point can be obtained by interpolation. If the value of the intermediate point is greater than the two intersection points, the value of the P point is unchanged, otherwise, the value is set to zero.

And performing hysteresis threshold operation on the noise reduction image after non-maximum suppression to obtain a boundary diagram. For example, two thresholds t1 and t2 may be set, t1 being equal to the number of boundary pixels divided by the total number of pixels, these points being referred to as weak edge pixels, t2 being equal to t1 times 2, the point between t2 and t1 being referred to as weak edge pixels. Finally, integrating the 8-connected weak pixels into the strong pixels, and connecting the strong pixels to obtain a boundary map.

In addition, the boundary map may be binarized. The effect of the method almost depends on the selection of the segmentation threshold, so that the image is divided into a background part and a target part according to the gray characteristic of the image, the segmentation with the largest inter-class variance between the background and the target means that the error probability value is the smallest, and an adaptive threshold is obtained through an algorithm and used as a binary segmentation basis.

After binarization, boundary refinement can also be performed on the boundary map. Since the detection result is severely affected by non-relevant pixels near the elliptical arc, a refined boundary is obtained by morphological erosion operations in order to greatly reduce non-relevant pixels.

At block 1404, the computing device 1010 performs boundary clustering on the boundary map to obtain a boundary clustering result.

Boundary clustering may include: boundary pixel connection, line segment column extraction, line segment column rotation direction unification, concave-convex point detection and segmentation, circular arc clustering and re-pairing.

Boundary pixel connection: and scanning the binary image from top to bottom and from left to right according to an 8-neighborhood communication rule, connecting boundary pixels into directed boundary columns, and then removing a set with smaller pixel numbers by adopting a pixel number threshold condition in the boundary columns. Since if the number of boundary column pixels is less than the threshold number, it is likely to be noise or background, it should be deleted. The specific steps may include: 1) Scanning the binary image from top to bottom and from left to right according to an 8-neighborhood communication criterion, and clustering pixel points in the image according to a communication area; 2) Searching all end points and bifurcation points (bifurcation points are intersection points of more than three curves) in boundary pixels in each connected domain and storing the same; 3) Dividing the pixel point set in each connected domain into small sets which are disconnected when encountering the ending point and the connecting point by taking the ending points and the bifurcation points as ending marks; 4) Portions of the sets having a number of pixels less than a certain threshold are deleted.

Line segment column extraction: because accurate tangent lines are difficult to obtain by image rasterization, tangent lines of circular arcs are needed in the subsequent process, and line segment fitting is performed, namely a plurality of sections of broken lines are used for replacing the original circular arcs. The method comprises the following specific steps: 1) Taking the ith directional boundary column formed by connecting boundary pixels, judging whether the total number of the boundary columns is exceeded, and if not, performing the step 2; if so, the algorithm is terminated. 2) Judging whether the boundary column is processed or not, if not, carrying out the step 3; if yes, i=i+1, and step 2 is performed again. 3) Calculating a connection equation from the first point to the third point (marked as point j), sequentially judging the distances from all points between the first point and the point to the connection, if all the distances are smaller than a certain threshold value, j=j+1, and carrying out step 3 again, otherwise, the directed boundary column is disconnected from the third point, the front part only keeps the first point and the j point, and the connection formed by the j points is replaced by a straight line connection between the first point and the j point; the latter part is still denoted as boundary column i. 4) Judging whether the pixel number of the rear part of the broken directed boundary column in the step 3 is smaller than a certain threshold value, if so, deleting, otherwise, not processing. Finally, the process jumps to step 1. After this process is completed, the curve formed by the pixels of the connected domain becomes a broken line formed by some of the pixels. Although a part of pixel information is lost through the process, the accuracy of obtaining the arc tangent is improved in a sense because no rasterization effect is generated. And the processing becomes simple with less data. And removing shorter line segment columns by adopting a threshold value condition of the number of line segments. If the number of line segments is less than the threshold number, the number is likely to be noise or background or the error in fitting is too large, and therefore the number must be deleted.

The rotation directions of the line segment columns are unified: the rotation directions of all the line segment columns are unified into the anticlockwise direction. Assuming that P1 (x 1, y 1), P2 (x 2, y 2), P3 (x 3, y 3) are three consecutive pixels in the line segment column, the pixels all introduce z-coordinates and let it be 0, then P1 (x 1, y1, 0), P2 (x 2, y2, 0), P3 (x 3, y3, 0).

Spatial vector:

P1P2＝(x2-x1，y2-y1，0)

P2P3＝(x3-x2，y3-y2，0)

vector product:

calculating, judging and storing all points except for the first and the last points in a line segment column like a P2 point, if the number of times is most less than 0, considering the rotation direction of the line segment column to be clockwise, and processing the points in the line segment column in an inverse sequence; if the number of times greater than 0 is the largest, the rotation direction of the segment columns is considered to be counterclockwise.

Pit and corner detection: after the rotation direction of the line segment column is determined to be anticlockwise, the method for detecting the concave points and the corner points is similar to the rotation direction of the line segment column unified in the front, P1P 2X P2P3 is calculated for all points except for the first point and the last point in one line segment column, the size of a third component of the vector product is judged, and if the size is smaller than 0, P2 is the concave point. Since boundary fluctuation may introduce redundant pits, that is, the detection rate is reduced due to the fact that the boundary detection error may misjudge some normal points as pits, an angle judgment process is added, that is, the front vector product is 0 and the included angle between P1P2 and P2P3 is greater than a certain threshold value, so that pits are only pits, and the accuracy of pit detection can be ensured by selecting a proper threshold value. If the vector product is greater than 0 and the included angle between P1P2 and P2P3 is greater than another threshold, the point is considered to be an angular point, and the line segment column is highly likely to be a corner of a pattern such as a triangle, a rectangle, or the like instead of an elliptical arc, so that the line segment column is divided from the point. After the segmentation is completed, the line segment columns with less points are filtered, and part of non-elliptical arcs can be removed. The remaining columns of line segments are considered as elliptical arcs, joining in subsequent clusters. As in fig. 3, P2 in the upper left corner is likely to be a pit and P2 in the lower right corner is likely to be a corner point.

And (3) arc clustering: two or more elliptical arcs belonging to the same ellipse but separated are clustered. Before clustering, the integrity of the arc segments is first determined. The determination is generally performed by the magnitude of the angle between the two vectors P2P1, P2P3 formed by the end points P1, P3 and the midpoint P2 of the arc segment. The smaller the included angle, the more complete the elliptical arc, and the larger the included angle, the more serious the elliptical arc defect is generally considered. And setting a threshold value, and considering that the arc section is complete enough when the included angle is smaller than the threshold value, and fitting the true ellipse accurately by only the points on the arc section, so that the arc section does not need to participate in the subsequent clustering process. If this threshold adaptation is desired, the threshold is determined before dividing the elliptical arcs to be clustered and the arcs that do not need to be clustered (more complete arcs). Fitting the ellipse of the arc by a direct least square method, and if the ellipse is round, for reducing the error, making the included angle of the threshold slightly larger, such as 90 degrees; if the ellipse in which the arc is located is relatively flat, the threshold angle should be made slightly smaller, for example 60 degrees. Then, the arc is judged according to the adaptive threshold value. When the value is larger than the threshold value, the points on the arc segment are considered to be too few, so that the accurate ellipse is not fitted, the arc segment which belongs to the same ellipse with the arc segment needs to be found, and then all points of the arc segment are used for fitting an ellipse together. Through this judgment process, the elliptical arcs are divided into two groups. The elliptical arcs needing to participate in clustering are arranged according to the number of points from more to less, and the following processes are all carried out according to the order of the priority of the arc segments with more numbers.

For an elliptical arc to be clustered, a search area is defined, and because the ellipse is a closed graph, the whole ellipse can be determined to be in an area surrounded by rays in which any part of the ellipse and tangents of two end points of the arc are located, and other arcs belonging to the ellipse are determined to be in an area surrounded by rays in which the corresponding chord of the arc and tangents of two end points of the arc are located. This is the area we search for. In fig. 15, the search area of a1, that is, the areas within the areas of rays l1, l2, chord l3 and image edges, and the arcs are found in this area, the search area can be reduced, and the efficiency can be improved. Judging whether an arc is in the search area of the elliptical arcs to be clustered or not, and only taking whether the head and tail end points j3 and j4 of the arc are in the search area or not. The method is that intersection points of straight lines and tangent lines which are parallel to corresponding chords l3 of elliptical arcs to be clustered are respectively obtained, if two intersection points are respectively obtained, the intersection points are both on rays, and the arc section is in a search area when the two end points are between the two corresponding intersection points. In fig. 15 it is evident that a2, a3, a4 are within the search area of a1 and a5 is not.

After the elliptical arcs to be clustered find the circular arcs to be paired, judging whether the elliptical arcs to be clustered belong to the same ellipse or not by using two constraint conditions. The constraint one is that the distance between the middle points of any two sections of arcs of an ellipse is larger than the distance between the middle point of one arc and the middle point of the connecting line of the head end point and the tail end point of the other arc, and in fig. 16, the distance is P1P2> P1C2 &p1P2> P2C1, which is used for removing the elliptic arc of the a2 type in fig. 15. In fig. 16, the right graph (b) does not satisfy the requirement, and the left graph (a) satisfies both the relationships, and the next step is performed, and the judgment is performed by using the constraint two.

And the constraint II is a condition of distance from a point to a fitted ellipse boundary, and only the points in the two line segment columns are needed to participate in ellipse fitting together, and the distances from all the points to the fitted ellipse boundary are calculated according to the following formula. A distance threshold is set and when di is less than the threshold the point is considered to lie on the ellipse, otherwise the point is not on the ellipse. And counting the number of points smaller than a certain threshold value in di, if the number is larger than a certain proportion (proportion threshold value), considering that the two arcs belong to the same ellipse, otherwise, not belong to the same ellipse, and clustering the arc sections belonging to the same ellipse together after judgment.

x'＝(x _i -x ₀ )cosθ+(y _i -y _O )sinθ

y'＝-(x _i -x ₀ )sinθ+(y _i -y ₀ )cosθ

As in fig. 17 (a) above, more points involved in the fitting fall on the ellipse of the fitting, so that it is more likely that the constraint two conditions are satisfied; (b) Most fitting points are at a certain distance from the fitted elliptical boundary, and the constraint condition II is likely to be unsatisfied.

If the two thresholds are hoped to be changed into self-adaption, the method is to fit an ellipse first and judge the size of the ellipse. If the ellipse is smaller, the limit should be properly reduced, i.e. the distance threshold is increased, and the proportion threshold is reduced; if the ellipse is large, the limit should be properly raised, i.e. the distance threshold is reduced and the ratio threshold is increased. For example, if the minor axis of the ellipse is less than 50, the distance threshold is 0.05 and the ratio threshold is 0.7; otherwise, the former takes 0.03 and the latter takes 0.8.

And (5) pairing: the clustered arcs and the more complete arcs or the two more complete arcs may belong to the same ellipse but in the previous step they are just separated and not paired, so it is necessary to add a re-matching process, increasing the detection accuracy. The matching method is also a constraint two method. Because the method is similar to the de-pseudo process of the original algorithm, the de-pseudo process is not needed after the method is carried out.

Returning to FIG. 14, at block 1406, the computing device 1010 performs an ellipse fit to the boundary cluster results to obtain an ellipse.

Many of the previous steps remove a smaller set of pixels, or replace many points in the border columns with a few points, or remove a smaller set of points after segmentation, and these operations to ellipse fitting steps remove virtually all background and noise, including even a portion of useful information. Even a direct least squares method sensitive to noise and outliers can be used to fit the ellipse and is very suitable because it is insensitive to elliptical defects.

At block 1408, the computing device 1010 determines a point in the region of interest with the smallest maximum distance from a point on the outline of the ellipse as the pupil center.

Let the image have an ellipse, point c be the center of the ellipse (the pupil center of the human eye), take point p (different from point c) on the plane, the maximum distance of point p from the point on the ellipse must be greater than the maximum distance of point c from the point on the ellipse. By calculating the distance L from each point in the image furthest from the ellipse (ellipse boundary), where the point where L is smallest is the center of the ellipse and L is the minor axis a of the ellipse. The core idea of the algorithm is that the center of the ellipse (the center of the pupil of the human eye) is the point with the smallest maximum distance from the point on the ellipse outline among all the points on the plane.

Therefore, the change of the shape of the cornea of the human eye in the rotating process can be detected through oval detection, so that the pupil center can be accurately determined.

Fig. 18 shows a schematic diagram of an example of a method 1800 for generating a corneal topography, in accordance with an embodiment of the disclosure. In fig. 18, various actions may be performed, for example, by the computing device shown in fig. 10. It should be appreciated that method 1800 may also include additional actions not shown and/or may omit actions shown, the scope of the present disclosure being not limited in this respect.

At block 1802, the computing device 1010 performs a gaussian convolution on the placido disc aperture image over a meridian passing through a predetermined center, resulting in a convolution result. The convolution formula I and gaussian function g can be shown as follows, where f is the gray scale distribution function over the meridian. As shown in fig. 19, the right half meridian 1902 is a ray that starts at a predetermined center, and the left half meridian is not shown.

I(x)＝g(x)*f(x)

At block 1804, the computing device 1010 determines a plurality of local peaks in the convolution result. The convolution results for the right semi-meridian may be as shown in fig. 20, with the local peaks in fig. 20 representing the locations of the apertures.

At block 1806, the computing device 1010 fits gray values for a predetermined number of pixels in a line segment that intersects each local peak to obtain a plurality of fitted curves.

For example, a line segment may be defined across each segment peak, including a predetermined number of pixels. The predetermined number includes, for example, but is not limited to, 6, i.e., the width of a single aperture. For example, a parabolic curve can be fitted by the taylor formula. As shown in fig. 21, the gray values of 6 pixels are fitted, and the resulting fitted curve is shown in fig. 22.

At block 1808, computing device 1010 determines the location at which the maximum gray value of each fitted curve is located as the ring center pixel point location. As shown in fig. 21, the position where the maximum gray value is located may be the ring center pixel position, that is, the center pixel position of the plurality of pixels occupied by the aperture.

At block 1810, the computing device 1010 determines an average of a plurality of ring center pixel point positions corresponding to a plurality of apertures within a predetermined number of rings as a placido disk aperture center.

The predetermined number of rings includes, for example, but is not limited to, 4, 5, 6, 7.

At block 1812, the computing device 1010 obtains pixels at ring center pixel point locations on each aperture at predetermined angles on polar coordinates of the placido disk aperture center as feature points.

For example, pixels at the positions of central pixel points of the rings on each optical ring can be acquired at intervals of 1 degree and used as characteristic points, so that the integrity of the whole cornea data information is ensured.

At block 1814, computing device 1010 generates a corneal topography map based on the acquired plurality of feature points.

For example, a point cloud model may be employed: accurate quantification of the corneal surface is described. Any suitable method may be used to recover the three-dimensional information from the acquired two-dimensional data of the feature points, where each point of the point cloud includes a local curvature, height, radial distance, etc.

As shown in fig. 23, M is the light source point on the Placido disc, C is the reflection point on the cornea, P is the lens center, and I is the corresponding point on the imaging screen. The radius of the point C sought can be replaced by the radius of the standard sphere corresponding to the same radius ring by comparison with the ring size on the Placido image of the standard sphere. The mapping between the radius of the ring/aperture on the Placido image of the standard sphere and the radius of the standard sphere may be, for example, pre-acquired.

The above approach introduces spherical aberration, as shown in fig. 24, with the standard sphere radius replacing the required point radius: the light incident from the light source point M is reflected into the camera lens through the point B on the cornea and the point A on the sphere, namely A, B points can reflect the same light into the lens to form the same Placido image; while the axial radius of A, B points is substantially the same, but at different heights and horizontal distances. If the position of the point A on the sphere is used for replacing the position of the point B on the cornea, spherical deviation is introduced at the moment, and incorrect height and horizontal distance are obtained, so that the calculation of local curvature is affected. Therefore, the method using the spherical reference cannot obtain an accurate height and a local radius of curvature.

The individual reflection points can be connected by smooth arcs, so that the discrete points are connected with each other and are not isolated. By adjusting the radius of these arcs so that each reflection point can reflect light into the lens, the constraints of the fixed arc length and reflection law are such that there is only a series of reflection points for a particular Placido disk. And non-circular curves can be better described in this way because, starting from the second reflection point, their centers may not be on the axis, where the radius of curvature at the reflection point truly represents the local radius of curvature of the curve.

Fig. 25 is a schematic diagram of an arc length iterative algorithm. The reflection points are connected by arcs with fixed radius, and the tangential direction of the previous arc is used as the initial direction of the arc at the reflection points, so that smooth connection of the arcs at the reflection points is ensured. Such constraints enable the location of unique reflection points to be determined while relatively accurate local curvature and height values can be obtained, avoiding transitions between different curvatures.

Specifically, the radius of the standard sphere corresponding to the radius of the aperture where each feature point is located may be determined as the radius of the reflection point corresponding to each feature point based on the mapping information between the radius of the aperture and the radius of the corresponding standard sphere. The radius of the aperture where each feature point is located can be determined, for example, by the distance between each feature point and the center of the aperture of the placido disc. Then, a plurality of reflection points corresponding to the feature points are acquired based on the radii of the reflection points corresponding to the feature points.

The first feature point may be determined from a plurality of feature points. The first feature point may be randomly determined from among a plurality of feature points, or from among feature points at the outermost ring or the innermost ring. And determining a first reflection point from the plurality of reflection points corresponding to the first characteristic point. The first reflection point may be determined, for example, randomly.

Next, for each second feature point adjacent to the first feature point, a second reflection point connectable to the first reflection point through an arc of a predetermined radius is determined from among a plurality of reflection points corresponding to the second feature point. The predetermined radius includes, for example, but is not limited to, 7.8mm, 7.9mm, 8mm, etc.

The following steps are iteratively performed until all feature points are traversed: for each third feature point adjacent to the second feature point, a third reflection point which can be connected with the second reflection point through an arc of a predetermined radius is determined from a plurality of reflection points corresponding to the third feature point, and the initial direction of the arc is the tangential direction of the last arc.

Based on the determined reflection points, a corneal topography is generated. After each reflection point is determined, the local curvature, height, radial distance and other information of each reflection point can be determined, and a cornea topographic map is generated.

Thus, for pixel-level center positioning obtained by using a circular detection algorithm, the above method satisfies the accuracy requirement of the corneal topography by convoluting, fitting and positioning the ring center of the sub-pixel with the average of the coordinates of the inner aperture (since the innermost ring does not break) within a predetermined number of rings such as 5 rings, for the problem that the ring center of the pixel cannot satisfy the accuracy requirement of the system because the corneal topography error cannot exceed 0.5D for the diopter change of the innermost ring single pixel width corresponding to 1.23 to 1.76D. In addition, through arc length iteration, spherical deviation can be eliminated, the position of a unique reflection point is determined, meanwhile, relatively accurate local curvature and height values can be obtained, and conversion between different curvatures is avoided.

Fig. 26 schematically illustrates a block diagram of an electronic device 2600 suitable for use in implementing embodiments of the present disclosure. Device 2600 may be used to implement computing device 1010 of fig. 10. As shown, the device 2600 includes a Central Processing Unit (CPU) 2601, which can perform various suitable actions and processes in accordance with computer program instructions stored in a Read Only Memory (ROM) 2602 or loaded from a storage unit 2608 into a Random Access Memory (RAM) 2603. In the RAM2603, various programs and data required for operation of the device 2600 may also be stored. The CPU 2601, ROM2602, and RAM2603 are connected to each other through a bus 2604. An input/output (I/O) interface 2605 is also connected to bus 2604.

Various components in device 2600 are connected to I/O interface 2605, including: an input unit 2606 such as a keyboard, a mouse, or the like; an output unit 2607 such as various types of displays, speakers, and the like; a storage unit 2608, such as a magnetic disk, an optical disk, or the like; and a communication unit 2609, such as a network card, modem, wireless communication transceiver, or the like. The communication unit 2609 allows the device 2600 to exchange information/data with other devices through a computer network such as the internet and/or various telecommunications networks.

The processing unit 2601 performs the various methods and processes described above, e.g., performs the

methods

1100, 1200, 1300, 1700. For example, in some embodiments, the

methods

1100, 1200, 1300, 1700 may be implemented as a computer software program stored on a machine readable medium, such as the storage unit 2608. In some embodiments, some or all of the computer programs may be loaded and/or installed onto device 2600 via ROM2602 and/or communication unit 2609. When the computer program is loaded into RAM 2603 and executed by CPU 2601, one or more operations of

methods

1100, 1200, 1300, 1700 described above may be performed. Alternatively, in other embodiments, the CPU 2601 may be configured to perform one or more actions of the

methods

1100, 1200, 1300, 1700 in any other suitable manner (e.g., by means of firmware).

The present disclosure may be methods, apparatus, systems, and/or computer program products. The computer program product may include a computer readable storage medium having computer readable program instructions embodied thereon for performing aspects of the present disclosure.

The computer readable storage medium may be a tangible device that can hold and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: portable computer disks, hard disks, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static Random Access Memory (SRAM), portable compact disk read-only memory (CD-ROM), digital Versatile Disks (DVD), memory sticks, floppy disks, mechanical coding devices, punch cards or in-groove structures such as punch cards or grooves having instructions stored thereon, and any suitable combination of the foregoing. Computer-readable storage media, as used herein, are not to be construed as transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., optical pulses through fiber optic cables), or electrical signals transmitted through wires.

The computer readable program instructions described herein may be downloaded from a computer readable storage medium to a respective computing/processing device or to an external computer or external storage device over a network, such as the internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers and/or edge servers. The network interface card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium in the respective computing/processing device.

Computer program instructions for performing the operations of the present disclosure can be assembly instructions, instruction Set Architecture (ISA) instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, c++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions may be executed entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, aspects of the present disclosure are implemented by personalizing electronic circuitry, such as programmable logic circuitry, field Programmable Gate Arrays (FPGAs), or Programmable Logic Arrays (PLAs), with state information of computer readable program instructions, which can execute the computer readable program instructions.

Various aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer-readable program instructions.

These computer readable program instructions may be provided to a processing unit of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processing unit of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable medium having the instructions stored therein includes an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer, other programmable apparatus or other devices implement the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The foregoing description of the embodiments of the present disclosure has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvement of the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for generating a corneal topography, comprising:

acquiring a plurality of first backlight loop images aiming at the same cornea, wherein the plurality of first backlight loop images are acquired at a plurality of positions in the preset eye axis direction by an axial stepping motor moving image acquisition device;

determining the number of pixels occupied by the width of the backlight loop in each first backlight loop image;

fitting the determined number of pixels to a parabola with an upward opening;

determining the position of an axial stepping motor corresponding to the lowest point of the parabola;

controlling the axial stepping motor to move from a preset zero position to the determined axial stepping motor position, and collecting a plurality of second backlight loop images of the target cornea, wherein the second backlight loop images have diaphragms with different diameters; and

Generating a corneal topography based on the plurality of second back-light ring images;

wherein acquiring a plurality of second back-light ring images of the target cornea is accomplished using a corneal topographer, wherein the corneal topographer comprises a projection device based on corneal reflection and an imaging module,

the projection device based on cornea reflection comprises a light source mechanism, a platy projection disk and a first movement mechanism, wherein the light source mechanism is provided with a light output end, the light source mechanism is used for outputting a hollow cone light beam taking a preset eye axis as an axis at the light output end and projecting annular light on a first side of the projection disk, and the first movement mechanism is used for shrinking and expanding the annular light by adjusting the relative position between the light output end and the projection disk in the preset eye axis direction; a cornea positioned on the second side of the projection disk receives the annular light to form reflected light, and the reflected light can be changed in light path after passing through the reflecting part of the projection disk; the reflecting part is positioned at the center of the annular light and is coaxial with the annular light;

the imaging module is used for receiving the reflected light and generating image information, the imaging module comprises a spectroscope element, an imaging lens group and an image sensor, the reflected light is reflected into the imaging lens group through the spectroscope element, and the imaging lens group focuses light on the image sensor; and

Collecting a plurality of second backlight loop images of the target cornea comprises controlling the first movement mechanism to drive a light output end of the light source mechanism and the projection disc to move relatively for a first distance in the direction of the preset eye axis, and controlling the imaging module to shoot the cornea positioned on the second side of the projection disc and obtain the plurality of second backlight loop images.

2. The method of claim 1, wherein controlling the imaging module to capture a cornea located on a second side of the projection disk and obtain the plurality of second back-lit images comprises:

acquiring a region of interest for a placido disc aperture; and

and controlling the imaging module to shoot the cornea positioned on the second side of the projection disc and obtaining a plurality of second backlight ring images, so that the diaphragms with different diameters are positioned in the region of interest.

3. The method of claim 2, wherein acquiring a region of interest for a placido disc aperture comprises:

acquiring a plurality of third back-light ring images for the same cornea, the plurality of third back-light ring images comprising apertures of different diameters;

determining a number of a plurality of diameter pixels of a plurality of diaphragms;

Determining a maximum diameter pixel number of the plurality of diameter pixel numbers; and

and determining the region of interest based on the maximum diameter pixel number and a preset offset.

4. The method of claim 3, wherein determining a plurality of diameter pixel numbers for a plurality of apertures comprises:

performing the following steps for each third backlight collar image of the plurality of third backlight collar images:

performing binarization processing on the third backlight loop image to generate a binary image;

detecting a connected circular area in the binary image;

filling the connected circular region with a predetermined pixel value; and

the number of pixels having a predetermined pixel value on the diameter of the filled connected circular area is determined as the number of diameter pixels of the diaphragm.

5. The method of claim 1, prior to acquiring the plurality of second back-porch images of the target cornea, the method further comprising:

acquiring an eye image including the target cornea;

determining a lateral pixel offset and a longitudinal pixel offset between a pupil center point in the eye image and a center point of an interface of the image acquisition device;

determining a lateral movement step number of a lateral stepper motor of the image acquisition device and a longitudinal movement step number of a longitudinal stepper motor of the image acquisition device based on a predetermined relationship between a lateral movement distance of the image acquisition device and a pixel movement distance of an imaging point in the interface, the lateral pixel shift, and the longitudinal pixel shift; and

And controlling the transverse stepping motor to move the transverse movement steps and the longitudinal stepping motor to move the longitudinal movement steps.

6. The method of claim 2, wherein generating a corneal topography map comprises:

performing offset correction on the plurality of second backlight loop images to obtain a plurality of offset corrected second backlight loop images;

superposing the plurality of offset corrected second back light ring images to generate a placido disk aperture image; and

generating a corneal topography based on the placido disc aperture image.

7. The method of claim 6, wherein offset correcting the plurality of second backlight loop images comprises:

for each of the plurality of second backlight collar images, performing the steps of:

performing circular detection in the region of interest;

if a circle is detected in the region of interest, taking the center of the detected circle as the pupil center; and

if no circle is detected in the region of interest, elliptical detection is performed in the region of interest to determine the elliptical center of the corresponding aperture as the pupil center; and

and aligning the centers of a plurality of pupils corresponding to the plurality of second backlight loop images to a preset center to obtain a plurality of second backlight loop images subjected to offset correction.

8. The method of claim 7, wherein performing circular detection within the region of interest comprises:

smoothing the second backlight loop image to generate a smoothed second backlight loop image;

performing binarization processing on the smoothed and filtered second backlight loop image to generate a binarized second backlight loop image;

determining a region for circular detection in the binarized second backlight loop image based on a maximum pixel number range and a minimum pixel number range which are acquired in advance; and

and carrying out circular detection in the determined area for circular detection and fitting based on the preset sensitivity value.

9. The method of claim 6, wherein generating a corneal topography map comprises:

carrying out Gaussian convolution on the placido disc aperture image on a meridian passing through a preset center to obtain a convolution result;

determining a plurality of local peaks in the convolution result;

fitting gray values of a preset number of pixels in a line segment penetrating through each local wave crest to obtain a plurality of fitting curves;

determining the position of the maximum gray value of each fitting curve as the position of the ring center pixel point;

Determining an average value of a plurality of ring center pixel point positions corresponding to a plurality of diaphragms in a preset ring number, and taking the average value as the diaphragm center of the placido disk;

acquiring pixels at the positions of the central pixel points of the rings on each diaphragm at intervals of a preset angle on the polar coordinates of the diaphragm center of the placido disk, and taking the pixels as characteristic points; and

a corneal topography is generated based on the acquired plurality of feature points.

10. The method of claim 9, generating a corneal topography map comprising:

determining the radius of the standard sphere corresponding to the radius of the aperture where each characteristic point is located based on mapping information between the radius of the aperture and the radius of the corresponding standard sphere, and taking the radius of the standard sphere as the radius of the reflection point corresponding to each characteristic point;

acquiring a plurality of reflection points corresponding to each feature point based on the radius of the reflection point corresponding to each feature point;

determining a first feature point from the plurality of feature points;

determining a first reflection point from a plurality of reflection points corresponding to the first feature point;

for each second feature point adjacent to the first feature point, determining a second reflection point which can be connected with the first reflection point through an arc with a preset radius from a plurality of reflection points corresponding to the second feature point;

the following steps are iteratively performed until all feature points are traversed: for each third feature point adjacent to the second feature point, determining a third reflection point which can be connected with the second reflection point through the circular arc with the preset radius from a plurality of reflection points corresponding to the third feature point, wherein the initial direction of the circular arc is the tangential direction of the previous section of circular arc; and

Based on the determined reflection points, a corneal topography is generated.

11. An electronic device, comprising:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein, the liquid crystal display device comprises a liquid crystal display device,

the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-10.

12. A non-transitory computer readable storage medium storing computer instructions for causing a computer to perform the method of any one of claims 1-10.