CN111803025B - Portable cornea topographic map acquisition system - Google Patents
Portable cornea topographic map acquisition system Download PDFInfo
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- 210000004087 cornea Anatomy 0.000 title claims abstract description 112
- 238000010191 image analysis Methods 0.000 claims abstract description 23
- 230000000007 visual effect Effects 0.000 claims abstract description 7
- 238000012876 topography Methods 0.000 claims description 49
- 210000001508 eye Anatomy 0.000 claims description 41
- 238000005070 sampling Methods 0.000 claims description 25
- 230000003287 optical effect Effects 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 17
- 238000003384 imaging method Methods 0.000 claims description 16
- 238000013461 design Methods 0.000 claims description 12
- 210000005252 bulbus oculi Anatomy 0.000 claims description 10
- 238000004458 analytical method Methods 0.000 claims description 4
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- 229910000831 Steel Inorganic materials 0.000 description 7
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- 210000000744 eyelid Anatomy 0.000 description 4
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- 210000003128 head Anatomy 0.000 description 2
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- 238000005259 measurement Methods 0.000 description 2
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- 201000002287 Keratoconus Diseases 0.000 description 1
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- 238000013399 early diagnosis Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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- 230000004424 eye movement Effects 0.000 description 1
- 230000010365 information processing Effects 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/107—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for determining the shape or measuring the curvature of the cornea
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/14—Arrangements specially adapted for eye photography
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/14—Arrangements specially adapted for eye photography
- A61B3/15—Arrangements specially adapted for eye photography with means for aligning, spacing or blocking spurious reflection ; with means for relaxing
- A61B3/154—Arrangements specially adapted for eye photography with means for aligning, spacing or blocking spurious reflection ; with means for relaxing for spacing
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Abstract
The invention relates to an acquisition system for handheld recording of cornea information, which comprises a projection part (101), a lens group (103), a camera (104) and an image analysis system (105), wherein the projection part (101) consists of an LED backlight source (111) and a Placido disk, the inner surface of the Placido disk is a uniform concentric ring with alternating black and white, light rays emitted by the LED backlight source (111) are blocked by the black part in the ring and transmitted to a measured cornea (112) through the white part in the ring, the interior of the Placido disk adopts a rotationally symmetrical arbitrary surface shape, the opening part of the Placido disk facing to the measured cornea (112) is enlarged as much as possible so as to facilitate processing the interior of the Placido disk, and light rays reflected from the measured cornea (112) are imaged through the lens group (104). The acquisition system has better visual field and image quality, and is convenient for obtaining the shape change rule of the cornea shape.
Description
Technical Field
The invention belongs to the field of cornea topographic map information acquisition, and particularly relates to an acquisition system for recording cornea information by hand.
Background
The refractive power of the cornea accounts for about 75% of the refractive power of the entire eye, so small changes in the morphology of the cornea will affect the refractive state distribution of the entire eye, directly affecting the eye's visual function. The detailed knowledge of the surface morphology of the cornea not only can help understand the pathological and physiological changes of the cornea, but also has very important significance in early diagnosis, treatment, prognosis evaluation and other aspects of cornea lesions (such as keratoconus and limbal cornea degeneration) mainly based on cornea ground change. The cornea topography instrument is used as an important measuring instrument in modern ophthalmic medical detection, and can display the surface topography of the cornea in the form of data or images, so that the cornea topography instrument becomes a powerful means for an ophthalmologist to measure the surface topography of the cornea and assist in cornea refractive surgery treatment.
The existing cornea topography collection system generally comprises a cornea topography instrument and an electronic computer, wherein the cornea topography instrument is composed of a projection disc, a camera and a control platform. The cornea topography instrument can project a plurality of concentric rings with the diameters from large to small onto the cornea of the human eye, the ring images reflected on the cornea are collected by the camera, and finally the collected information is transmitted to the computer for analysis and calculation to obtain the topography data of the cornea surface of the human. Existing corneal topographer projection discs are generally divided into two categories: the number of the circular rings of the disc type projection system is small, and the number of the circular rings of the cone type projection system is large. The more the rings, the more data points the computer can collect, the more accurate the fit to the corneal topography. Existing corneal topography acquisition systems typically analyze only a single image, and are not capable of analyzing real-time changes in the cornea as the shape of the cornea of the human eye may be deformed by changes in the eyelid eye. Meanwhile, the existing cornea topographic map instrument has poor portability and can only be collected in a hospital.
Therefore, there is a need for a portable corneal topography acquisition system that has good image quality and facilitates obtaining a pattern of corneal shape changes that is a function of eye movement and eyelid snap.
Disclosure of Invention
The invention aims to provide a portable cornea topography acquisition system which can acquire cornea information of different sizes.
The portable cornea topography collection system of the present invention comprises: a projection part (101), a lens group (103), a camera (104) and an image analysis system (105), wherein the components consisting of the projection part (101), the lens group (103) and the camera (104) are handheld parts, wherein the projection part (101) consists of an LED backlight source (111) and a Placido disc, the inner surface of the Placido disc is a uniform concentric ring with alternate black and white, light emitted by the LED backlight source (111) is blocked by a black part in the ring and transmitted to a measured cornea (112) through a white part in the ring, and the interior of the Placido disc adopts a rotationally symmetrical arbitrary surface shape, wherein the Placido disc is enlarged as much as possible towards an opening part of the measured cornea (112) so as to process the interior of the Placido disc, the light reflected from the measured cornea (112) is imaged through the lens group (104), and a generated corneal topography is recorded by the camera (104); the image analysis system (105) is stored in an external processor of the hand-held part, and the quality of the measured cornea (112) is obtained by analyzing the generated cornea topography with the image analysis system (105).
In one aspect of the portable corneal topography acquisition system of the present invention, the hand-held portion is a hand-held anti-shake cradle head (102).
In one aspect of the portable corneal topography acquisition system of the present invention, wherein the camera (104) comprises a Charge Coupled Device (CCD), the imaging location is located 1 focus out of the lens assembly (103) and 2 focus in and a clear image is obtained when the photosensitive element CCD/CMOS is placed in the imaging location.
One aspect of the portable corneal topography acquisition system of the present invention, wherein the interior of the Placido disc is tapered, elliptical or hyperbolic in cross-section.
In one aspect of the portable corneal topography acquisition system of the present invention, wherein the design of the Placido disc inner surface when the Placido disc interior is tapered in cross section follows the following formula: the lens group (103) and the tip part of the conical section are overlapped at the point (A) of the lens optical center; further, the distance between the C point of the inner ring of the Placido disk and the optical center A of the lens is represented by L, and the position of the C point accords with the following formula:
combining equations (4) and (6):
wherein r is the radian of the cornea; θ is 180 degrees- α - β; alpha isBeta is 180- & lt- & gt> Is that
Gamma is the internal angle of the cone; y is the distance from the center of the lens to the center of the corneal arc;
l is the distance from the optical center A to the point C of the inner ring of the disk cone.
In one aspect of the portable cornea topography acquisition system, light rays are emitted from a point C on the inner ring of a conical body of a Placido disk to a point B on a detected cornea (112) and then reflected to a point A on an optical center of a lens group (103), finally reach a point D on a CCD, and under the condition that the radian of the detected cornea (112) is consistent with the design radian, concentric circles on the Placido disk are mapped to the detected cornea (112) for reflection and then reflected to the CCD to form equidistant concentric circles.
In one aspect of the portable corneal topography acquisition system of the present invention, the CCD is 32 parts.
In one aspect of the portable corneal topography acquisition system of the present invention, wherein the design of the Placido interior surface follows the following formula when the Placido interior is elliptical in cross-section:
in one embodiment, the following elliptic equation is used:
wherein x and y are xy coordinate values of an ellipse; a is half of the long axis; b is half of the minor axis, the zero position of the coordinates is at the center point of the ellipse.
In one aspect of the portable corneal topography acquisition system of the present invention, the Placido disc is processed to a precision of at least 0.01mm.
In one aspect of the portable cornea topographic map acquisition system, the rear surface of the Placido disk is uniformly illuminated, so that white light-transmitting stripes and black light-blocking stripes in black and white concentric rings form concentric rings with alternate brightness and uniform illumination, the contrast between adjacent stripes is enhanced, and under the basic requirement of guaranteeing visual safety, the wavelength of the LED light source has high reflectivity to the surface of the cornea and enough luminous intensity.
In one aspect of the portable cornea topography acquisition system of the present invention, the LED light source is an AlGalnP red LED having a diameter of 3mm, and has a dominant wavelength of 625nm and a luminous intensity of 400mcd. In one aspect of the portable cornea topographic map acquisition system of the present invention, the LED light source is configured to freely adjust the brightness of the red LED and the center of the light panel has a circle of green LEDs to attract the attention of the eyes of the subject to obtain a stable center position of the eyeball, and the green LEDs may be configured to have different lighting modes, such as continuous lighting, intermittent lighting, simultaneous flashing, etc.
In one aspect of the portable cornea topography acquisition system, light rays are emitted from a point C on the inner ring of a Placido disk cone to a point B on a detected cornea (112) and then reflected to a point A on an optical center of a lens group (103), finally, the light rays reach a point D on a CCD, and under the condition that the radian of the detected cornea (112) is inconsistent with a designed radian, concentric circles on the Placido disk are mapped to the detected cornea (112) for reflection and then reflected to the CCD, the concentric circles shot on the CCD have deviation, and the radian of the cornea is reversely deduced from the positions of the concentric circles.
One aspect of the portable corneal topography acquisition system of the present invention, wherein the image analysis system comprises:
the alignment module aligns the image center of the acquisition system with the human eye center before the acquisition system shoots, and meanwhile, the human eye is positioned at a specified shooting distance to acquire and analyze the image; the position adjusting module is used for drawing an auxiliary circle in the displayed image when shooting, the position adjusting is operated by an acquisition operator, and when the circle image reflected on human eyes is overlapped with the circle on the displayed image, the system automatically judges that the position is a proper shooting position; the distance judging module is used for judging whether the human eyes are at a proper distance according to the definition of the images, and when the central position and the distance meet the requirements, the system starts to acquire the images of the human cornea; the projection module is used for extracting sampling points after the image sensor receives the image, wherein each sampling point is the projection of a specific projection ring at a specific angle; and the sampling point analysis module calculates the normal angle of the sampling point, and the corresponding curvature change and other parameters can be obtained after the sampling point is fitted to the curved surface.
In one aspect of the portable corneal topography acquisition system of the present invention, the lens assembly (103) is a telescopic lens structure, and is composed of at least two lenses; the first screw rod structure (108) stretches into the lens group (103), the lens group (103) can be driven to move along the horizontal direction, and along with rotation of the motor (107), the first screw rod structure (108) can help the lens group (103) to zoom at any time.
In one aspect of the portable cornea topography acquisition system of the present invention, wherein the image obtained by the lens assembly (103) is coaxial with the camera (104), the camera (104) is positioned on the slide (106), the camera (104) moves along with the second screw structure (108') along the horizontal direction by the driving of the second motor (107), thereby focusing with the lens assembly (103), when the cornea with different size is acquired, the lens assembly adjusts the field of view by automatic focusing, and because the distance between the cornea and the lens is fixed, when the observed cornea is detected to be smaller, the focal length and the position of the camera are adjusted, so that the cornea image is enlarged to a proper size.
The invention relates to a portable cornea topographic map acquisition system and a method for acquiring and obtaining a cornea topographic map, wherein: before the acquisition system shoots, an operator aligns the center of an image of the acquisition system with the center of human eyes, and meanwhile, the human eyes are positioned at a specified shooting distance to acquire and analyze the image; drawing an auxiliary circle in the displayed image when shooting, performing position adjustment by an acquisition operator, and automatically judging the system as a proper shooting position when the circle image reflected on human eyes is overlapped with the circle on the displayed image; the image analysis system judges whether the human eyes are at a proper distance according to the definition of the images, and when the central position and the distance meet the requirements, the system starts to collect the images of the human eyes cornea; after the image sensor receives the image, sampling point extraction is carried out, and each sampling point is the projection of a specific angle of a specific projection ring; and calculating the normal angle of the sampling point, and fitting the sampling point to the curved surface to obtain corresponding parameters such as curvature change. The portable cornea topographic map acquisition system has good visual field, good image quality and convenient acquisition of the shape change rule of cornea shape caused by eyeball movement and eyelid instantaneous movement.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below. It will be apparent to those skilled in the art that the drawings in the following description are merely examples of the invention and that other drawings may be derived from them without undue burden to those skilled in the art.
Fig. 1 (a) is a schematic diagram of the structure of the acquisition system of the present invention.
Fig. 1 (b) is a schematic diagram of an imaging portion of one embodiment of an acquisition system of the present invention.
Fig. 2 (a) - (b) are block diagrams of an optical imaging section involving a lens group in the acquisition system of the present invention.
Fig. 3 (a) is a schematic diagram of an optical imaging portion of the collection system of the present invention involving a lens group.
Fig. 3 (b) is a basic optical schematic diagram of an optical imaging section involving a lens group in the collection system of the present invention.
Fig. 4 (a) is a front view of a structure of an embodiment of the acquisition system of the present invention involving a projection disk.
Fig. 4 (b) is a schematic diagram of an embodiment of a projection disk as referred to in the acquisition system of the present invention.
Fig. 4 (c) is a cross-sectional view A-A of another embodiment of the acquisition system of the present invention involving a projection disk configuration.
Fig. 4 (d) is a right side view of another embodiment of the acquisition system of the present invention involving a projection disk structure.
Fig. 4 (e) is a simulation of the effect of an embodiment of the elliptical cross-section processing of the projection disk of the acquisition system of the present invention.
Fig. 4 (f) is a schematic view showing the effect of an embodiment of the invention in which the projection disk of the acquisition system is machined according to an elliptical cross section.
FIG. 4 (g) is a schematic drawing of a projected disk elliptical cross-section processing of the acquisition system of the present invention.
Fig. 5 is a flowchart of the operation of the image analysis system of the acquisition system of the present invention.
Fig. 6 (a) schematically shows a block diagram of a server for performing the method according to the invention; and
fig. 6 (b) schematically shows a memory unit for holding or carrying program code for implementing the method according to the invention.
Detailed Description
Specific embodiments of the present invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention.
Fig. 1 (a) is a schematic diagram of the structure of the acquisition system of the present invention. The acquisition system 100 includes a projection component 101, a handheld anti-shake head 102, a lens group 103, a camera 104, and an image analysis system 105. The projection disc 101 is located on the handheld anti-shake holder 102, the lens set 103 is movably mounted in front of the camera 104 under the control of the motor 107 through the slide rail 106, the image analysis system 105 is an information processing part of the acquisition system 100, and the shape change rule of the cornea shape along with eyeball movement and eyelid snap motion can be obtained by analyzing based on the video acquired by the camera 104 by being mounted in the acquisition system 100. The manual anti-shake holder 102 is optional, and the projection disc 101, the lens group 103 and the camera 104 may be placed on a common handheld device and operated under the control of the image analysis system 105.
Fig. 1 (b) is a schematic diagram of an imaging portion of one embodiment of an acquisition system of the present invention. Wherein the acquisition system comprises a charge coupled device (CCD, not shown), which is located in the camera (104); the projection unit 101 includes an LED backlight 111 and a Placido disk 110, and the Placido disk 110 has an inner surface in the form of uniform black and white concentric rings, with an opening facing the spherical cornea 112. The working principle between the lens group 103 and the projection part 101 and the measured cornea 112 is described in detail below. The CCD is used for recording the corneal topography of the measured cornea (112).
Fig. 2 (a) - (b) are block diagrams of an optical imaging section involving a lens group in the acquisition system of the present invention. Fig. 2 (a) is a block diagram of a zoom portion of a lens group of an acquisition system according to the present invention. Wherein, the lens group 103 is a sleeve type lens structure and consists of at least two lenses; the first screw structure 108 stretches into the lens group 103, can drive the lens group 103 to move in the horizontal direction, and along with rotation of the motor 107, the first screw structure 108 can help the lens group 103 to zoom at any time; fig. 2 (b) is a block diagram of a focusing portion of the lens group of the collecting system of the present invention. Wherein the zoom portion of the lens group 103 is not shown; the image obtained by the lens group 103 is coaxial with the camera 104, the camera 104 is positioned on the slideway 106, and the camera 104 moves along with the second screw structure 108' along the horizontal direction by the driving of the second motor 107, so as to be focused with the lens group 103.
When different sized corneas are collected, the lens will adjust the field of view by auto-focusing, because the cornea-to-lens front distance is fixed, the focal length and camera position will be adjusted to enlarge the cornea image to the proper size when the observed cornea is detected to be small. In one embodiment, the lens group 103 may also be held in a fixed relationship with the handheld device.
Fig. 3 (a) is a schematic diagram of an optical imaging portion of the collection system of the present invention involving a lens group. The focal length and the field of view of the existing acquisition system are fixed. One embodiment of the present invention increases the field of view by focusing, i.e., focusing, the acquisition system. In the working process of the acquisition system, the focal length of the lens group is not changed, but the image distance, namely the distance between the imaging surface and the lens is changed through adjustment, so that the distance from the imaging surface to the optical center is equal to the image distance, and an object can be clearly imaged on a film (a photosensitive element). The process of adjusting the camera to make the subject a clear image is called a focusing (focusing) process. For example, the imaging position is located outside the lens by 1 time focal length and within the lens by 2 times focal length, and the imaging position is the position where the photosensitive element CCD/CMOS is located, and the imaging is very clear. If the imaging position deviates from the plane of the photosensitive element CCD/CMOS, the imaging becomes very virtual and is more fuzzy, namely the focusing inaccuracy phenomenon during shooting occurs.
Zooming is another way of expanding the field of view for an acquisition system, and is to change the focal length of a lens, so that the visual angle or the image size is changed, and the zooming-in or zooming-out effect is obtained. Typically by variations in lens combinations. The longer the focal length, the narrower the viewing angle, and the fewer views that can be accommodated in the picture, the closer the picture looks. The shorter the focal length, the larger the viewing angle, and the more scenes can be accommodated in the picture, the farther the picture appears.
Fig. 3 (b) is a basic optical schematic diagram of an optical imaging section involving a lens group in the collection system of the present invention. The object dimension 204 may be represented by the symbol x, the image dimension 207 may be represented by the symbol x ', the distance 206 between the imaging location and the optical center 208 may be represented by the symbol f', and the distance 205 between the object and the optical center 208 may be represented by the symbol L. Equation (1) of the basic optical principle is as follows:
that is, the larger the vertical distance f ', the larger the imaged dimension 207, i.e., x'. FIG. 4 (a) isThe acquisition system of the present invention relates to a structural front view of one embodiment of a projection disk. The projection disk in the acquisition system of the invention is an improvement on Placido disk in the existing cornea topographic information acquisition system. The Placido disk is used for projecting equidistant concentric rings on the cornea of an eye, and is designed by a steel ball with the same radius of curvature as the cornea.
Light emitted by the LED backlight source is diffusely reflected to illuminate eyeballs at a certain distance, black and white stripes on the Placido disk are projected onto the cornea, and the light is reflected by the cornea and imaged on a charge coupled device ("CCD") through a lens system. In the case of no lesions on the surface of the cornea, the images are concentric circles and the distance between the rings is evenly distributed. If the surface topography of the cornea is abnormal, the image is oval, and the distance between the rings is uneven. The smaller curvature of the surface of the cornea, the farther the distance between adjacent rings in the radial direction; the portions of the corneal surface with greater curvature have smaller radial spacing between adjacent rings, similar to topographical contour measurements. By analyzing the degree of deformation of the concentric rings on the image, the change of the corneal curvature at different positions can be obtained, thereby further analyzing the diopter at various positions of the cornea.
The Placido disk is composed of a series of concentric rings with black and white alternate, white is a transparent part, black is a non-transparent part, and a small hole is arranged in the center for placing an imaging element. Light emitted by the LED backlight source is diffusely reflected to illuminate eyeballs at a certain distance, and black and white stripes on the Placido disk are projected onto the cornea.
The ideal Placido disk is a hemispherical body concentric with the steel ball, equidistant circular rings are arranged on the disk, and the image projected on the steel ball is the equidistant concentric circular rings. Typical Placido disk surfaces include conical, spherical and ellipsoidal. The number of the conical concentric circles is relatively large, the arrangement of the rings is relatively dense, the measurement data points are dense, and the processing precision requirement is very high; the spherical processing is relatively simple, but the cornea measuring range is small, the precision is not high and the device volume is large; the number of the ellipsoidal concentric rings is relatively small, the processing precision requirement is relatively low, and the ellipsoidal concentric rings have good measuring precision. In order to match the portability of the present invention, the projection disk of the present invention adopts any rotationally symmetrical surface shape. In order to realize any rotationally symmetrical surface shape, firstly, a method of adopting a conical section, an elliptic section or a hyperbolic section in the inner part is adopted, so that the caliber of an opening part of the Placido disk facing to a measured corner film (112) is enlarged as much as possible, and the Placido disk is convenient to process, thereby solving the problem that the processing difficulty is increased due to the narrow space of the inner ring of the small-opening cone.
Fig. 4 (b) is a schematic diagram of an embodiment of a projection disk as referred to in the acquisition system of the present invention. The C point is the position of the inner ring of the Placido disc, the distance L represents the distance between the C point and the optical center A of the lens, and the position of the C point is designed by using the following formula:
combining equations (4) and (6):
wherein r is the radian of the cornea; θ is 180 degrees- α - β; alpha isBeta is-> Is->
Gamma is the internal angle of the cone; y is the distance from the center of the lens to the center of the corneal arc;
l is the distance from the optical center A to the point C of the inner ring of the disk cone.
The design principle is based on a simplified calculation model by overlapping the lens center and the conical tip at the optical center A. Wherein the point D is the position of the CCD, the point A is the optical center of the lens, and the point C is the position point of the inner ring of the Placido disk cone; and the point B is a steel ball surface position point simulating eyes. The cone inner ring of the projection disk is designed into uniform concentric rings. In one embodiment, it is split into 32 sections on the CCD.
In the process of measuring the radian of the cornea, light is beaten onto the eyeball, namely a steel ball simulating the eyeball, and the steel ball is an ideal sphere and has a certain difference from a real cornea of the eyeball; but can simulate the shape of the cornea of an eyeball to some extent; in fig. 4 (B), light is emitted from point C of the cone of the Placido disk to point B on the measured cornea (112), and then reflected to point a of the optical center of the lens group (103), and finally reaches point D on the CCD, where the radian of the measured cornea (112) is consistent with the design radian, the concentric circles on the Placido disk are mapped onto the measured cornea (112) to reflect light, and then reflected onto the CCD, so that equidistant concentric circles are formed, and if the radian is different, the positions of the concentric circles photographed on the CCD have deviations. The curvature of the cornea can be deduced back from the position of the concentric circles. The spacing and size of the rings captured on the CCD will vary with the amount of corneal curvature, and the spacing will be the same only if the corneal angle is the same as the design curvature. The radian is small, the radian is large, and the distance between the circles is non-equidistant.
In another embodiment, the elliptical shape of FIG. 4 (g) is formed by processing with the following elliptical equation:
wherein x and y are xy coordinate values of an ellipse; a is half of the long axis; b is half of the minor axis. The zero position of the coordinates is at the center point of the ellipse.
Fig. 4 (c) is a cross-sectional view A-A of another embodiment of the acquisition system of the present invention involving a projection disk configuration. As shown, the interior of the Placido disk is oval. Fig. 4 (d) is a right side view of the acquisition system of the present invention involving a projection disk configuration. As can be seen from fig. 4 (c) and 4 (d), with the same opening size, a better processing of the inner loop line can be obtained with an elliptical or hyperbolic cross section. This is also shown in fig. 4 (e), where fig. 4 (e) is a schematic view of the processing effect of the projection disk of the acquisition system according to the present invention according to an elliptical cross section. The arc design is easier to process than the linear design, and the measuring precision is better. Fig. 4 (f) is a schematic view showing the effect of an embodiment of the invention in which the projection disk of the acquisition system is machined according to an elliptical cross section. FIG. 4 (g) is a schematic drawing of a projected disk elliptical cross-section processing of the acquisition system of the present invention.
After the surface type data and the ring distribution of the Placido disk are determined, proper processing technology and processing method need to be selected for processing production. Resolution is required to reach sub-pixels in the final image processing, so that Placido discs are processed to a precision of at least 0.01mm. The normal cornea surface should be equidistant concentric circles, and can be monitored without concentric circles in relation to the later curvature calculation method. Fig. 4 (f) is an effect diagram of processing according to an elliptical cross section. Wherein the steel ball 202 is a simulated eye lens, is positioned at the front part of the eye 201, and the Placido disk is processed along the ellipse 203, so that a better visual field can be obtained.
Furthermore, a small-opening projection disk has the problem that an image of a person in a deep eye socket cannot be acquired, and thus the opening together is enlarged to a diameter of 80mm, i.e., the vertical axis in the above formula is changed to 80mm.
The acquisition system of the invention also comprises a freely adjustable LED illuminating lamp plate. In order to meet the imaging requirement of CCD, the back surface of the Placido disk needs to be uniformly illuminated, so that white light-transmitting stripes and black light-blocking stripes in black-and-white concentric rings form concentric rings with alternate brightness and uniform illumination, the contrast between adjacent stripes is greatly enhanced, the stripes on the Placido disk are easier to observe during image acquisition, the image processing work is easier to carry out, and the acquired edge sampling point data are more accurate. The spectrum sensitivity characteristic of the SONY ICX424AL type CCD and the spectrum light efficiency of the photopic vision of human eyes reach the highest at about 550nm, but the green light still has good penetration rate in normal eye refraction medium, which is about 80%. Therefore, under the basic requirement of ensuring visual safety, the wavelength of the LED light source is required to have not only high reflectivity to the surface of the cornea but also sufficient luminous intensity. The invention can adopt AlGalnP red LED with the diameter of 3mm as a light source light-emitting element, the dominant wavelength is 625nm, the light-emitting intensity is 400mcd, and the invention has the characteristics of good monochromaticity, high brightness, high light-emitting efficiency, long service life and the like, has higher spectral sensitivity to CCD, and simultaneously has high reflectivity to cornea without damaging eyes. However, the single LED lamp has low light energy output and large divergence angle when used as a near lambertian body for emitting light, and uniformity cannot be ensured.
The collecting system can freely adjust the brightness of the red LEDs, and the lamp panel is provided with a circle of green LEDs at the center, so that the green LEDs can attract the attention of the eyes of a tested person to obtain a stable eyeball center position, and different lighting modes such as continuous lighting, interval lighting, simultaneous flashing and the like can be set, so that the collecting system can better attract the attention of the tested person.
Fig. 5 is a flowchart of the operation of the image analysis system of the acquisition system of the present invention. In step 301, before shooting, the acquisition system needs an operator to align the center of an image of the acquisition system with the center of human eyes, and meanwhile, the human eyes are located at a specified shooting distance to acquire and analyze the image. In step 302, an auxiliary circle is drawn in the displayed image during shooting, the position adjustment is operated by an acquisition operator, and when the circle image reflected on the human eyes is overlapped with the circle on the displayed image, the system automatically judges that the system is at a proper shooting position; in step 303, the image analysis system determines whether the human eye is at a suitable distance according to the sharpness of the image, and when the central position and the distance meet the requirements, the system starts to collect the image of the cornea of the human eye. After the image sensor accepts the image, a sample point is extracted, and each sample point is projected at a particular angle from a particular projection ring, step 304. In step 305, the normal angle of the sampling point is calculated, and the corresponding parameters such as curvature change can be obtained after fitting the sampling point to the curved surface. According to the steps, the image analysis system of the acquisition system can realize the functions of judging, recording and analyzing the image conditions to generate the topographic map.
Fig. 6 (a) is a block diagram of an image analysis system of the acquisition system of the present invention. The acquisition system requires an operator to align the image center of the instrument with the human eye center when shooting, and meanwhile, the human eye is positioned at a specified shooting distance to acquire and analyze the image. When shooting, an auxiliary circle is drawn in the displayed image, the position adjustment is operated by an acquisition operator, when the circle image reflected on the human eyes is overlapped with the circle on the displayed image, the system automatically judges the proper shooting position, in addition, the image analysis system judges whether the human eyes are at a proper distance according to the definition of the image, and when the central position and the distance meet the requirements, the system starts to acquire the cornea image of the human eyes. After the image sensor accepts the image, sampling point extraction will be performed, with each sampling point being a projection at a particular angle for a particular projection ring. The normal angle of the sampling point can be calculated, and parameters such as corresponding curvature change and the like can be obtained after the sampling point is fitted to the curved surface. The image analysis system of the acquisition system can realize the functions of judging, recording and analyzing the image conditions to generate the topographic map, and the recorded data can be transferred to a computer for further analysis.
The image analysis system comprises a server 501 of the image analysis system. The server of the image analysis system comprises a processor 510, which here may be a general purpose or application specific chip (ASIC/ASIC) or FPGA or NPU, etc., and a computer program product or computer readable medium in the form of a memory 520. The memory 520 may be an electronic memory such as a flash memory, an EEPROM (electrically erasable programmable read only memory), an EPROM, a hard disk, or a ROM. Memory 520 has storage space 530 for program code for performing any of the method steps described above. For example, the memory space 530 for the program code may include respective program code 531 for implementing the respective steps in the above method, respectively. These program codes may be read out or written into the processor 510. These computer program products comprise a program code carrier such as a hard disk, a Compact Disc (CD), a memory card or a floppy disk. Such a computer program product is typically a portable or fixed storage unit as described with reference to fig. 6 (b). The storage unit may have a memory segment, a memory space, or the like arranged similarly to the memory 520 in the server of fig. 6 (a). The program code may be compressed, for example, in a suitable form. Typically, the storage unit comprises computer readable code 531', i.e. code that can be read by a processor, such as 510, for example, which when run by a server causes the server to perform the steps in the method described above. The code, when executed by a server, causes the server to perform the steps in the method described above.
Reference herein to "one embodiment," "an embodiment," or "one or more embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Furthermore, it is noted that the word examples "in one embodiment" herein do not necessarily all refer to the same embodiment.
The above description is only for the purpose of illustrating the technical solution of the present invention, and any person skilled in the art may modify and change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, the protection scope of the invention should be considered as the scope of the claims. The invention has been described above with reference to examples. However, other embodiments than the above described are equally possible within the scope of the disclosure. The different features and steps of the invention may be combined in other ways than those described. The scope of the invention is limited only by the appended claims. More generally, one of ordinary skill in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention are used.
Claims (15)
1. A portable corneal topography acquisition system comprising:
a projection part (101), a lens group (103), a camera (104) and an image analysis system (105), wherein the components consisting of the projection part (101), the lens group (103) and the camera (104) are handheld parts, wherein the projection part (101) consists of an LED backlight source (111) and a Placido disc, the inner surface of the Placido disc is a uniform concentric ring with alternate black and white, light emitted by the LED backlight source (111) is blocked by a black part in the ring and transmitted to a measured cornea (112) through a white part in the ring, and the interior of the Placido disc adopts a rotationally symmetrical arbitrary surface shape, wherein the Placido disc is enlarged as much as possible towards an opening part of the measured cornea (112) so as to process the interior of the Placido disc, the light reflected from the measured cornea (112) is imaged through the lens group (103), and a generated corneal topography is recorded by the camera (104); wherein the lens group (103) is of a sleeve type lens structure and consists of at least two lenses; the first screw rod structure (108) stretches into the lens group (103) and can drive the lens group (103) to move along the horizontal direction, and the first screw rod structure (108) can help the lens group (103) to zoom at any time along with the rotation of the motor (107);
-the image analysis system (105) is stored in an external processor of the hand-held part, the quality of the measured cornea (112) being obtained by analyzing the generated corneal topography with the image analysis system (105); comprising the following steps:
the alignment module aligns the image center of the acquisition system with the human eye center before the acquisition system shoots, and meanwhile, the human eye is positioned at a specified shooting distance to acquire and analyze the image;
the position adjusting module is used for drawing an auxiliary circle in the displayed image when shooting, the position adjusting is operated by an acquisition operator, and when the circle image reflected on human eyes is overlapped with the circle on the displayed image, the system automatically judges that the position is a proper shooting position;
the distance judging module is used for judging whether the human eyes are at a proper distance according to the definition of the images, and when the central position and the distance meet the requirements, the system starts to acquire the images of the human cornea; the projection module is used for extracting sampling points after the image sensor receives the image, wherein each sampling point is the projection of a specific projection ring at a specific angle;
and the sampling point analysis module calculates the normal angle of the sampling point, and the corresponding curvature change and other parameters can be obtained after the sampling point is fitted to the curved surface.
2. The portable corneal topography acquisition system of claim 1, wherein
The hand-held part is a hand-held anti-shake holder (102).
3. The portable corneal topography acquisition system as in claim 1, wherein the camera (104) comprises a Charge Coupled Device (CCD), the imaging location is located 1 x out of the focal length and 2 x in the focal length of the lens assembly (103), and a clear image is obtained when the photosensitive element CCD/CMOS is placed in the imaging location.
4. The portable corneal topography acquisition system of claim 3, wherein
And the Placido disk has an interior with a conical, elliptical or hyperbolic cross-section.
5. The portable corneal topography acquisition system of claim 4, wherein when the interior of the Placido disc is tapered in cross section, the design of the Placido disc interior surface follows the following formula: the lens group (103) and the tip part of the conical section are overlapped at the point (A) of the lens optical center; further, the distance between the C point of the inner ring of the Placido disk and the optical center A of the lens is represented by L, and the position of the C point accords with the following formula:
combining equations (4) and (6):
wherein r is the radian of the cornea; θ is 180 degrees- α - β; alpha isBeta is-> Is that
Gamma is the internal angle of the cone; y is the distance from the center of the lens to the center of the corneal arc;
l is the distance from the optical center A to the point C of the inner ring of the disk cone.
6. The portable corneal topography system as in claim 5, wherein the light rays are emitted from point C of the cone inner ring of the Placido disk to point B of the measured cornea (112) and reflected to point a of the optical center of the lens assembly (103) and finally to point D of the CCD, and the concentric circles on the Placido disk are mapped onto the measured cornea (112) to reflect light and then reflected onto the CCD to form equidistant concentric circles if the radian of the measured cornea (112) is consistent with the design radian.
7. The portable corneal topography acquisition system of claim 6, wherein the CCD is 32 parts.
8. The portable corneal topography acquisition system of claim 7, wherein when the interior of the Placido disc is elliptical in cross-section, the design of the Placido disc interior surface follows the following formula:
wherein x and y are xy coordinate values of an ellipse; a is half of the long axis; b is half of the minor axis, the zero position of the coordinates is at the center point of the ellipse.
9. A portable corneal topography acquisition system as in claim 3, wherein the Placido disc is processed to a precision of at least 0.01mm.
10. The portable corneal topography collection system of claim 1, wherein the posterior surface of the Placido disk is uniformly illuminated such that white light-transmitting stripes and black light-blocking stripes in black and white concentric rings form concentric rings of alternating brightness and uniform illumination, thereby enhancing contrast between adjacent stripes, and the LED backlight has a wavelength that is not only highly reflective to the corneal surface, but also sufficiently luminous intensity under the basic requirement of ensuring visual safety.
11. The portable corneal topography acquisition system of claim 10, wherein the LED backlight source is a 3mm diameter AlGalnP red LED having a dominant wavelength of 625nm and an emission intensity of 400mcd.
12. The portable corneal topography acquisition system of claim 10, wherein the LED backlight source is configured to freely adjust the brightness of a red LED and a circle of green LEDs is arranged in the center of the lamp panel to attract the attention of the eyes of the tested person so as to obtain a stable center position of the eyeball, and the green LEDs can be set to be lighted in a continuous type, a spaced type and a different lighting mode with flashing at the same time.
13. The portable corneal topography system as in claim 5, wherein the light rays are emitted from point C of the cone inner ring of the Placido disk to point B of the measured cornea (112) and reflected to point a of the optical center of the lens assembly (103) and finally to point D of the CCD, and in case the radian of the measured cornea (112) is inconsistent with the design radian, the concentric circles on the Placido disk are reflected to the CCD after being reflected to the measured cornea (112), the concentric circles shot on the CCD deviate, and the radian of the cornea is reversely deduced from the positions of the concentric circles.
14. The portable corneal topography acquisition system as in claim 13, wherein the image obtained by the lens assembly (103) is coaxial with the camera (104), the camera (104) is positioned on the slide (106), the camera (104) is moved along with the second screw structure (108') in a horizontal direction by the driving of the second motor (107) so as to be focused with the lens assembly (103), and when the cornea of different sizes is acquired, the lens assembly adjusts the field of view by auto-focusing, and because the cornea-to-lens distance is fixed, the focal length adjustment and the camera position are adjusted to enlarge the cornea image to a proper size when the observed cornea is detected to be small.
15. A method of acquiring and obtaining a corneal topography using the portable corneal topography acquisition system of claim 1, wherein:
before the acquisition system shoots, an operator aligns the center of an image of the acquisition system with the center of human eyes, and meanwhile, the human eyes are positioned at a specified shooting distance to acquire and analyze the image; drawing an auxiliary circle in the displayed image when shooting, performing position adjustment by an acquisition operator, and automatically judging the system as a proper shooting position when the circle image reflected on human eyes is overlapped with the circle on the displayed image;
the image analysis system judges whether the human eyes are at a proper distance according to the definition of the images, and when the central position and the distance meet the requirements, the system starts to collect the images of the human eyes cornea; after the image sensor receives the image, sampling point extraction is carried out, and each sampling point is the projection of a specific angle of a specific projection ring;
and calculating the normal angle of the sampling point, and fitting the sampling point to the curved surface to obtain corresponding parameters such as curvature change.
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| CN113240711B (en) * | 2021-05-08 | 2023-06-09 | 温州医科大学附属眼视光医院 | Real-time individual crosslinking system |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012116807A1 (en) * | 2011-03-03 | 2012-09-07 | Optocraft Gmbh | Method and device for topography measurement on the eye |
| CN102657512A (en) * | 2012-05-11 | 2012-09-12 | 浙江工业大学 | Image acquisition equipment applied to corneal topography instrument |
| DE102011102354A1 (en) * | 2011-05-24 | 2012-11-29 | Carl Zeiss Meditec Ag | System for determining surface shape of cornea of eye, has keratoscope, illuminating unit, image recording unit with telecentric image capturing and control- and evaluation unit |
| DE102014210787A1 (en) * | 2014-06-05 | 2015-12-17 | Carl Zeiss Meditec Ag | Distance-compensated measuring device for topographical and keratometric measurements on the eye |
-
2020
- 2020-05-12 CN CN202010398470.3A patent/CN111803025B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012116807A1 (en) * | 2011-03-03 | 2012-09-07 | Optocraft Gmbh | Method and device for topography measurement on the eye |
| DE102011102354A1 (en) * | 2011-05-24 | 2012-11-29 | Carl Zeiss Meditec Ag | System for determining surface shape of cornea of eye, has keratoscope, illuminating unit, image recording unit with telecentric image capturing and control- and evaluation unit |
| CN102657512A (en) * | 2012-05-11 | 2012-09-12 | 浙江工业大学 | Image acquisition equipment applied to corneal topography instrument |
| DE102014210787A1 (en) * | 2014-06-05 | 2015-12-17 | Carl Zeiss Meditec Ag | Distance-compensated measuring device for topographical and keratometric measurements on the eye |
Non-Patent Citations (1)
| Title |
|---|
| 隋成华 ; 沃圣杰 ; 徐丹阳 ; 高楠 ; 张玉民 ; .角膜地形图仪中Placido盘及投射照明系统的设计与实现.光学精密工程.2017,(第03期),全文. * |
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