KR20100058756A - Measurement method of corneal curvature with measurement position compensation and eye examining apparatus using the same - Google Patents

Abstract

PURPOSE: A method for measuring the curvature of a cornea with compensated measuring position errors, and an eye examining device using the same are provided to rapidly measure the curvature of a cornea by directly calculating the curvature from a focus light image. CONSTITUTION: An eye examining device comprises mire ring light sources(21a, 21b), focus light sources(26,27), an imaging optical system(30), and an calculation controller(40). The mire ring light sources irradiate a ring-shaped measuring light to a cornea(3) of an eye(1).The focus light sources are located in the center of the mire ring light sources, and irradiate two point-shaped measuring light to the cornea. The imaging optical system detects a mire ring optical image and a focus light image reflected from the cornea. The calculation controller calculates the diameter of the mire ring optical image and the distance of the focus light image, and compensates measuring position errors of the eye.

Description

Corneal curvature measuring method to compensate for the measurement position error and an optometry using the same {measurement method of corneal curvature with measurement position compensation and eye examining apparatus using the same}

The present invention relates to a corneal curvature measuring method and an optometry using the same, and more particularly, to a corneal curvature measuring method for automatically compensating a measurement position error of an eye to be examined by using a myring light and a focus light and an optometry using the same. .

The optometry is an optical device for measuring the state of the eye, such as refractive power and corneal curvature of the eye, and in particular, the optometry for measuring corneal curvature is an optoelectronic measuring system mainly composed of an optical part, an electronic part, and a mechanical part. The optical unit includes a light detection optical system including a light output optical system that emits a collimated light and a measurement light to the cornea of the eye to be examined, a mirror that changes the course of the light reflected by the cornea, and a light detection sensor that detects an optical signal. The optical detection sensor converts an optical signal into an electrical signal and transmits the optical signal to a central processing unit, and the central processing unit calculates corneal curvature values by applying a calculation algorithm for processing the same. The calculated corneal curvature value of the eye is a criterion for prescribing a contact lens suitable for the corneal shape of the eye, and when contact lenses of incorrect corneal curvature are worn, the contact lens flows down, a foreign body feels, Since it may cause scratches or inflammation, it is very important to obtain accurate corneal curvature values of the eye.

In measuring the curvature of the cornea of the eye, the optical detection optical system of the eyepiece is located when the eyepiece is located away from the eyepiece by a predetermined measurement distance, that is, when the eyepiece is located at the focal length of the optical system on the optical axis of the eyepiece optics. It is designed so that the measurement light reflected from the image is most accurately formed. However, it is not easy to determine the measurement position of the eye from the imaging state of the measurement light output on the monitor screen, and the distance between the eye and the eyepiece optics is different because it greatly depends on the eye movement of the eye during the measurement and the skill of the eye. However, it is important to calculate corneal curvature with minimal errors.

1 is a view for explaining an optometry with the aperture open in a conventional ophthalmoscope measuring the corneal curvature, Figure 2 is an optometrist with an aperture inserted in the optometrist measuring a conventional corneal curvature. It is a figure for demonstrating. As shown in Figs. 1 and 2, the conventional optometry optical system is reflected by a mirroring 20, which produces a ring-shaped measurement light pattern, light sources 21a and 21b of the measurement light, and cornea 3 of the eye to be examined. Measuring lens 31 for imaging the myring light on the two-dimensional photodetecting element 32, when measuring the eye to be inserted between the measuring lens 31 and the two-dimensional photodetecting element 32, A diaphragm 14 for restricting a path of an allergic light, an aperture motor 10 for driving the diaphragm 14, and an aperture motor 10 for driving the diaphragm 14 may be used. Computational control device 40 for calculating the corneal curvature value from the image.

The operation of an optometry for measuring a normal corneal curvature is as follows. First, the measuring light emitted from the light sources 21a and 21b passes through the ring 20 to form a shape of the ring in the cornea 3 of the eye to be examined, and the reflected light reflected from the cornea 3 of the eye to be examined. Is imaged on the two-dimensional light detecting element 32 by the measuring lens 31, and the arithmetic and control unit 40 outputs the image of the imaged miring on the monitor of the optometry. The optometrist observes the imaging state of the miring, adjusts the position of the optometrist so that the miring is clearly formed, and selects the start of measurement, the operation control device 40 drives the aperture motor 10, FIG. As shown in FIG. 14, the diaphragm 14 is inserted between the measuring lens 31 and the two-dimensional photodetecting element 32, and the remaining miring is covered by the diaphragm 14 while the periphery of the reflected light reflected from the cornea is blocked. The light is imaged onto the two-dimensional photodetection element 32. When the measurement distance of the eye is changed, as shown in FIG. 1, the size change of the missed miring in the opened aperture is the size of the missed miring in the inserted diaphragm as shown in FIG. 2. Greater than change Therefore, the arithmetic and control unit 40 compares the size of each miring when the diaphragm 14 is opened and when the diaphragm 14 is inserted, and calculates a focus error due to the measurement position of the eye, and compensates therefrom. The resulting corneal curvature can be calculated as a result.

The optical system of an optometry for measuring the corneal curvature of the conventional cornea is used to reflect the error of the cornea curvature value that is incorrectly calculated due to the change in the size of the miring when the eye is not positioned at the correct measuring distance of the optical system. An aperture 14 and an aperture motor 10 for implementing a telecentric effect on the ringing light are included. Therefore, in the case of the conventional optometry, the overall measurement time is calculated by calculating the size of the mirroring when the aperture is opened at the time of measurement, driving the aperture motor, inserting the aperture, and calculating the size of the missing mirroring. Since the measurement distance between the eye and the optometrist did not change before and after the aperture 14 was inserted, if the position of the eye was changed while inserting the aperture 14, an incorrect corneal curvature value would be calculated. In addition, there is a disadvantage in that it is not easy for the optometrist to determine the change in the position of the eye during the measurement. In addition, the diaphragm 14 and a precise motor 10 for driving the diaphragm and a control circuit for driving the diaphragm are required, which not only increases the production cost of the product, but also complicates the mechanical configuration. There is a disadvantage in that the measurement calculation error and the possibility of mechanical failure, which may occur due to the area where the measurement light is telecentric beyond the performance of the motor, are increased.

An object of the present invention is to provide a corneal curvature measuring method having a simple mechanical structure and an optometry using the same without the need for a separate measurement position error compensation device.

Another object of the present invention is to provide a method for measuring corneal curvature and an optometry using the same, wherein the position error compensation is accurate and rapid.

In order to achieve the above object, the present invention comprises a mirror ring light source for irradiating the ring-shaped measurement light to the cornea of the eye; A focus light source positioned at the center of the mirroring light source and irradiating the measurement light in the form of two dots to the cornea of the eye to be examined; An imaging optical system configured to detect a mirroring light image and a focus light image reflected from the cornea; And calculating a diameter (R) and a distance (F) of the focusing light image (R) of the mirroring light image, respectively, from the detected mirroring light image and the focusing light image, and compensating for the measurement position error of the eye to be examined. An optometry comprising an arithmetic and control device for measuring the curvature of the cornea of the eye to be examined from the image of the lighted light. In addition, the present invention comprises the steps of irradiating the measuring light and focus measurement light to the cornea of the eye to be examined, and detecting the light and the focus light image reflected from the cornea; Computing the diameter (R) and the distance (F) of the focusing light image in the measurement, the measurement (R) and the diameter (R) of the mirroring light image in the measurement Calculating a focus interval (D, D = RF) during measurement from the distance (F) of the focus light image; When the cornea of the eye to be examined is located at the focal length of the measurement light, the diameter of the mirroring light image and the distance of the focus light image are calculated, and the focus interval is calculated from the diameter of the mirroring light image and the distance of the focus light image, Deriving a relationship graph (L) of a diameter of the miring light image and the focus interval; Calculating a diameter (R ') of a reference-based miring light image corresponding to the focus interval (D) during the measurement in the graph (L); Calculating a focus error [Delta] Z, [Delta] Z = R-R 'from the diameter R of the miring light image during the measurement and the diameter R' of the miring light image at the reference; Determining whether the focus error ΔR is within an allowable range; A correction step of correcting a diameter (R) and a focus interval (D) of the measuring light image when the focus error (ΔR) is not within an allowable range; And measuring the corneal curvature of the eye to be examined from the diameter (R) of the miring light image when the focus error (ΔR) is within the allowable range.

Corneal curvature measuring method and the optometry using the same according to the present invention compensates the measurement position error by using the meerring light and focus light used for corneal curvature measurement provided in the optometry, Even if the measurement position of the eye is changed, accurate corneal curvature can be measured without focus error, and the corneal curvature is calculated directly from the imaging light and focus light image formed at the beginning of the measurement. There is no error due to the change of position, so it is possible to measure more quickly. In addition, the corneal curvature measuring method and the optometry using the same, there is no need for a separate position adjusting device and means, the mechanical structure is simplified, thereby reducing the manufacturing and maintenance costs.

Hereinafter, a method for measuring corneal curvature and an optometry using the same according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 3 is a view for explaining the structure of the optometry according to an embodiment of the present invention, Figure 4 is a view for explaining the myring light and focus light formed in the cornea in the optometry according to an embodiment of the present invention to be.

As shown in FIG. 3, an optometrist according to an embodiment of the present invention includes a mirroring optical system 20, an imaging optical system 30, and an operation control device 40. As a light transmitting means for transmitting the measurement light reflected from the imaging optical system 30 may include a reflection mirror and a relay lens.

The miring optical system 20 is for forming a myring light and a focus light for measuring the curvature of the cornea on the surface of the cornea 3 of the eye to be examined. A ring 28 to allow the ringing light to be radiated to the cornea 3 of the eye to be examined 1 by the ringing light sources 21a and 21b and the ringing light emitted from the ringing light sources 21a and 21b. Focus light sources 26a and 27b which are located at the centers of the light source 21a and 21b and generate focus light of one vertex to the left and right of the center of the mirroring 28 and the focus light sources 26 and 27. And collimation lenses 22, 23 which emit the focus light passing through the pinholes 24, 25 into parallel light. Ring-shaped light emitting devices (LEDs) may be used as the mirroring light sources 21a and 21b, and the same light emitting devices (LEDs) may be used as the focus light sources 26 and 27. Therefore, as shown in FIG. 4, the light of the light emitted from the light sources 21a and 21b forms a ring-shaped light of light image 101 on the cornea 3 of the eye to be examined 1, The focus light irradiated from the focus light sources 26 and 27 forms two focus light images 102 and 103 on the cornea 3 of the eye to be examined 1. The size of the mirroring light image 101 is represented by the diameter R of the mirroring light image 101, and the size of the focus light images 102 and 103 is the distance F of the focus light images 102 and 103. Represented by

The imaging optical system 30 is an imaging lens 31 and an imaging lens for forming an image on the photodetector 32 as a means for forming a myring light image and a focus light image reflected by the eye to be examined 1. And a photodetector 32 for converting the meering light image and the focus light image formed by 31) into an electrical signal. The photodetector 32 is connected to the arithmetic and control unit 40, and the image formed miring light image and the focus light image are transmitted to the arithmetic control device 40, whereby The corneal curvature value of the eye to be examined 1 is calculated. The photodetector 32 may be a conventional two-dimensional imaging device.

The arithmetic and control unit 40 is connected to the imaging optical system 30 and is a means for calculating corneal curvature from a meering light image and a focus light image detected by the imaging optical system 30. Compensation for the measurement position error of λ) and calculating corneal curvature values from the mirroring light image and the focus light image. The operation control device 40 compensates for the measurement position error of the eye to be examined 1 from the mirroring light image and the focus light image, and describes a method of measuring corneal curvature as follows. First, as shown in FIG. 4, when the eye 1 is positioned at the correct measurement distance of the eyepiece, it forms the brightest and clearest miring on the cornea 3 of the eye 1, The size of the miring is determined by the degree of curvature of the cornea of (1). If the eye 1 is located in front of or behind the measurement distance of the eyepiece, blurring occurs around the miring, and the sharpness and brightness of the miring are lowered, and the cornea of the eye 1 It becomes larger or smaller than the size of the miring determined according to the curvature, causing an incorrect corneal curvature value to be calculated. However, by the collimating lenses 22 and 23, the focus light, which is converted into parallel light and projected to the cornea, forms the focus light images 102 and 103 at a certain point on the cornea irrespective of the measurement position of the eye.

FIG. 5 is an eyepiece according to an embodiment of the present invention, in which the eye is positioned inside the focal length of the measurement light, when the eye is located at the focal length, and when the eye is located outside the focal distance, a miring light image and a focus light image A diagram for explaining. As shown in FIG. 5, the more the eye 1 is located inside the focal distance, based on the diameter Rb of the miring light image when the eye 1 is located at the focal length of the optical system measurement light. The larger the diameter Ra of the mirrored light image is, the smaller the diameter Rc of the mirrored light image is from the outside of the focal length. As a result, the relationship of "Ra> Rb> Rc" holds true for the diameter R of the said light beam image according to the positional relationship with respect to the focal length of the eye to be examined 1. On the other hand, in each case, the position of the focus light image remains constant, so that the distance F between the focus light images is almost the same. Therefore, when the eye 1 is positioned at the correct measurement distance of the eyepiece, the diameter R of the miring light image and the distance F of the focus light image increase in proportion to the corneal curvature of the eye 1. From this, the focus intervals D and D = RF, which are the difference between the "R" and "F", increase.

6 is a view for explaining the relationship between the diameter of the mirroring light image and the distance between the focus light image in the optometry according to the present invention. As shown in FIG. 6, The straight line "L" indicates the relationship between the diameter R of the miring light image and the distance D of the focus light image when the corneal curvature increases when the eye 1 is located at the focal length of the optical system measurement light. A straight line "M _k " represents the diameter R of the meering light image and the distance D of the focusing light image generated by the change of the measurement position of the eye to be examined when the curvature of the cornea is k. Represents a relationship. The intersection point 121 of the straight line “L” and the straight line “M _k ” is a diameter r _K and a focusing interval d of the miring light image when the eye 1 having the corneal curvature k is positioned at the correct measurement distance. _K ). Therefore, when measuring the eye with curvature of the cornea, the diameter r and the focus interval d of the actual miring light image detected from the imaging optical system 30 are located on the straight line "M _k ", and the straight line "L". Is used to calculate the diameter "r '" of the miring light image when the measurement distance is correct with respect to "d", and the difference "Δr" between "r" and "r'" is obtained. The degree of focus error and the degree of measurement position error can be determined. As the eye 1 becomes farther out of the focal length of the optical system, the diameter r of the miring light image decreases, and the intersection point on the straight line "M _k " of "r" and "d" is reduced. It changes in the left direction of 121, and "r" increases as the eye 1 becomes farther inward of the focal length, and changes in the right direction of the intersection 121. The straight line "L" calculates the diameter R of the miring light image and the distance F of the focus light image when the cornea 3 of the eye to be examined 1 is located at the focal length of the optical system measurement light, A focus interval D is calculated from the diameter R of the mirroring light image and the distance F of the focus light image, and a relationship between the diameter R of the mirroring light image and the focus distance D is derived. Can be obtained by

A method of compensating for a measurement position error of an eye to be examined by using the relational property of the diameter R and the focus distance D of the mirroring light image is as follows. 7A and 7B are diagrams for explaining a method of compensating for measurement position error of an eye under the eyepiece according to an embodiment of the present invention, when the eye is positioned outside the focal length and the focal distance of the measurement light. . That is, FIGS. 7A and 7B show the diameters of the miring light image calculated from the miring light image and the focus light image detected by the imaging optical system 30 when the eye is located outside the focal length and inside the focal distance of the measurement light, respectively. From (r) and the focus interval d, using the straight line "L" which is a corneal curvature change graph with respect to the diameter and focus interval of the miring light image shown in FIG. 6, and the straight line "M _k " which is a focus error graph, The process of correcting the measurement position error of the eye to be examined 1 and calculating the diameter r _K of the miring light image when the eye to be measured 1 is located at the correct measurement distance is shown. First, as shown in FIG. 7A, a description will be given based on a case in which the eye is positioned outside the focal length of the measurement light. When the measurement distance is correct from the straight line "L", that is, when the eye 1 is located at the focal length of the optical system measurement light, the diameter "r 'of the reference-based meering light image corresponding to the focus interval" d "at the time of measurement "Save. A focus error (Δr, Δr = r-r ') is calculated from the diameter r of the miring light image at the measurement and the diameter r' of the miring light image at the reference, and the focus error Δr is allowed. Determine if it is a possible error range. The focus error Δr refers to an amount of error made by the measurement position in the diameter of the mirroring light image, and the tolerance range refers to a range in which corneal curvature can be measured from the mirroring light image during measurement. Typically 0.54 mm to 0.72 mm. That is, if the focus error amount Δr is an allowable error range, the diameter r of the miring light image at the time of measurement is approximated to the diameter r _K of the miring light image obtained from the corneal curvature of the eye at the correct measurement distance. You can judge that.

When the focus error [Delta] r is outside the tolerance range, the reference focal length spacing "d '" when the measurement distance is correct is obtained for the diameter r of the miring light image at the time of measurement from the straight line "L". . The reference when focus distance "d '" to about focus error graph is a straight line "M _d'" the calculation, and the focus error graph is a straight line Real focus from "M _{d '"} interval "d" and a reference when focus distance "d "obtains" the difference (Δd, Δd = d'- d) the diameter (r of the steering Mai optical image when the focus error is corrected, the correction by "). that is, the straight line graph of the focus error" M _{d ""} From this, the diameter r "of the miring light image corresponding to the reference time focal length d 'is obtained. Therefore, when the focus error Δr is not within the tolerance range, the curvature of the cornea of the eye 1 may be measured based on the diameter r ″ of the corrected miring light image. Calculating (Δr), determining whether the focus error (Δr) is within an allowable range, and correcting the diameter (R) of the miring light image is performed by the eye to be examined 1 shown in FIG. 7B. The same applies to the case where it is located inside, so that the diameter "r" and the focusing interval "d '" of the newly calculated mirroring light image are converted into the diameter r and focusing distance d of the actual mirroring light image. By repeating the above procedure until the diameter r " of the meering light image becomes smaller within the tolerance range, instead of a), the focusing error due to the measurement position of the eye is sufficiently compensated. The diameter "r _K " can be calculated. The ophthalmoscope using the corneal curvature measuring method according to the present invention corrects the diameter of the miring light image based on the measured miring light image and the focus light image without the need for a separate measurement error correction device. Even if the position of the inside is changed, accurate measurement of the curvature of the cornea is possible, and rapid measurement becomes possible.

8 is a view for explaining a method of compensating measurement position error and a method of calculating a focus error graph "M _k " in an optometry according to an embodiment of the present invention. Referring to FIG. 8, a process of calculating the diameter “r _K ” of the compensated miring light image will be described using a formula. When the diameter "r _n " of the nth meering light image during the focus error correction process and the focus interval "d _n ", the equation of the straight line "L" is "y = px + q", The magnitude of the focus error "Δr _n " is as follows.

When the focus error "| Δr _n |" is out of tolerance, the reference focus interval "d _{n +1} " from the straight line "L" to the "r _n " is as follows.

The corneal curvature is "k _j " and "k _{j + 1} ", the focus interval at the correct measurement position is "d _j " and "d _{j + 1} ", and satisfies d _j <d _n <d _{j + 1} The equation of the line "M _j ", which is the focus error graph of two model eyes, is "y = a _j x + b _j ", and the equation of the line "M _{j + 1} " is "y = a _{j + 1} x ₊ b _j + ₁ "is called when the focus distance" d _{n + 1} "the slope of the focus error straight line (M _{dn + 1)} in the" _n k _{+ 1} "is as follows.

Diameter of the mirroring light image whose focus error is compensated by the focus interval difference "Δd _{n +1} " from the slope "k _{n + 1} " of the focus error straight line M _{dn + 1} at the focus interval "d _{n + 1} ". "r _{n +1} " is as follows.

It is determined whether the focus error Δr is within the allowable range by the diameter "r _{n + 1} " and the focus interval "d _{n +1} " of the new miring light image obtained from Equations (3) and (5), and the process is repeated. Thus, the diameter of the new miring light image and the distance of the focus light image can be obtained. In addition, the straight line "M _{dn + 1} " which is a focus error graph in the focus interval "d _{n + 1} " has a constant curvature "j, j ₁ ", as shown in FIG. 8, and "d _{n + 1} " The straight lines "M _j " and "M _{j +} obtained from the change in the measured position of the Model Eye showing the focal spacing (d _j , d _{j + 1} , d _j1 <d _{n + 1} <d _{j + 1} ) adjacent to Based on ₁ ", the focus interval" d _{n + 1} "is calculated | required by interpolation method.

A corneal curvature measuring method for compensating for a measurement position error according to an embodiment of the present invention will be described in detail. 9 is a flowchart of a method for measuring corneal curvature according to an embodiment of the present invention. In the corneal curvature measuring method for compensating for the measurement position error according to an embodiment of the present invention, determining whether the measurement position of the eye is an acceptable range, compensating for the measurement position error of the eye and measuring the curvature of the cornea (S 30).

Determining whether the measurement position is within the allowable range may include detecting a miring light image and a focus light image as illustrated in FIG. 9 (S 10); Calculating a diameter R of the miring light image and a distance F of the focus light image during the measurement, and calculating the focus intervals D and D = R-F during the measurement (S 12); Deriving a relationship graph L between a diameter of the miring light image and the focus interval (S 14); Calculating a diameter R ′ of the miring light image at reference S16; Calculating a focus error [Delta] R, [Delta] R = R-R '(S 17); And determining whether the focus error [Delta] R is in the allowable range (S 18). When the focus error [Delta] R is in the allowable range, the corneal curvature measurement step is continued, and the focus error [Delta] R is allowed. If it is out of range, a step is taken to compensate for the measurement position error.

The detecting of the miring light image and the focus light image (S 10) may include the cornea of the eye to be examined 1 through the lighter light sources 21a and 21b (see FIG. 3) and the focus light sources 26 and 27. 3) irradiating the measuring light and the focus measuring light, and the operation control device 40 to output the falling light image (101, Fig. 3) and the focus light image (102, 103) reflected from the cornea (3) Detecting at Computing the focus interval (D, D = RF) in the measurement step (S 12), the measuring light image from the measured light beam image 101 and the focus light image (102, 103), respectively Calculate the diameter (R) and the distance (F) of the focus light image, and from the diameter (R) of the miring light image and the distance (F) of the focus light image during the measurement, the focus interval (D, D = RF) is calculated. Deriving the relationship graph L between the diameter of the miring light image and the focus interval (S 14), when the cornea 3 of the eye 1 is located at the focal length of the measurement light, that is, When the eye to be examined 1 is located at the measurement position where the measurement is made accurately, the diameter of the mirroring light image and the distance of the focus light image are calculated, and the focus interval from the diameter of the mirroring light image and the distance of the focus light image. And calculating a relationship graph L between the diameter of the miring light image and the focus interval. The relation graph L is typically stored in the arithmetic and control unit 40. Computing the diameter (R ') of the reference eye image light (S 16), in order to confirm the measurement position error of the eye to be examined 1, in the relationship graph (L), the focus interval at the measurement Comprising (D) is the step of calculating the diameter (R ') of the reference vision meering light image. The calculating of the focus error (ΔR, ΔR = R-R ') (S 17) is a step of obtaining a measurement position error amount of the eye to be measured 1 during measurement, and the diameter of the meering light image during measurement ( From the R) and the diameter R 'of the reference light beam image, a focus error ΔR and ΔR = R-R' are calculated. Determining whether the focus error ΔR is an allowable range (S 18) is a step of checking whether the eye 1 belongs to a range in which accurate measurement is possible, and the allowable range is usually 0.54 mm to 0.72 mm. .

Compensating the measurement position error of the eye, the step of correcting the diameter of the miring light image, if the focus error ΔR is not within the allowable range, calculating a reference focal length D '(S) 20); Deriving a focus error graph M _{d '} (S 22); Calculating a diameter R ″ of the miring light image at the time of correction (S 24); and substituting the diameter R ″ of the miring light image at the time of correction and the focal length D ′ at the reference time. . The step S20 of calculating the reference focal length spacing D 'may include, in the relation graph L, a reference visual focal spacing D' corresponding to the diameter R of the miered light image during the measurement. It is a step of calculating. Deriving the focus error graph M _{d '} (S 22) refers to deriving a focus error graph M _{d ′} from the reference time focusing interval D ′, wherein the focus error graph M _{d ′} is derived. M _{d '} ) has a constant curvature, as shown in FIG. 8, and a focus interval D _j , D _{j + 1} , D _j1 <D'<D _{j + 1} ) adjacent to the focus interval D '. a not shown on the basis of the (model Eye) "M _j" straight line determined from the measured position change and the "M _{j + 1"} of the model, the focus interval is obtained by linear interpolation with respect to the "D '". Computing the diameter (R ") of the miring light image at the time of correction (S 24) is a step of obtaining a diameter of the miring light image compensated for the measurement position error, in the focus error graph (M _{d '} ) Computing the diameter R ″ of the miring light image for correction corresponding to the reference focal length D ′. Substituting the diameter R ″ and the reference focal length D ′ of the miring light image upon correction may include determining whether the diameter R ″ of the corrected miring light image falls within an acceptable range. As a step, the diameter R "and the reference focal length D 'of the correction miring light image are substituted into the diameter R and the focus interval D of the measuring light image, respectively, Computing the diameter (R ') of the reference reference mirroring light image, based on the diameter (R ") and the reference focusing interval (D') of the correction light image (S 16), focus error Calculating (ΔR, ΔR = R-R ') (S 17), and determining whether the focus error ΔR is within the allowable range (S 18) is repeated.

Measuring the corneal curvature (S 30), when the focus error (ΔR) is within the allowable range, from the diameter of the measuring light or the diameter of the measuring light to compensate for the measurement position error in the measurement Corneal curvature of the eye is measured. That is, the arithmetic and control device 40 calculates or corrects the corneal curvature value of the eye to be examined 1 from the diameter R of the myring light image detected by the imaging optical system 30 (see FIG. 3). The corneal curvature value of the eye to be examined 1 is calculated from the diameter R ″ of the miring light image. When the corneal curvature value is calculated, the corneal curvature measurement is finished.

BRIEF DESCRIPTION OF THE DRAWINGS The figure for demonstrating the optometry with the aperture open in the optometrist which measures the normal corneal curvature.

FIG. 2 is a view for explaining an optometry in a state where an aperture is inserted in an optometry for measuring a normal corneal curvature. FIG.

3 is a view for explaining the structure of the optometry according to an embodiment of the present invention.

4 is a view for explaining the myring light and focus light formed in the cornea in the optometry according to an embodiment of the present invention.

FIG. 5 is an eyepiece according to an embodiment of the present invention, in which the eye is positioned inside the focal length of the measurement light, when the eye is located at the focal length, and when the eye is located outside the focal distance, a miring light image and a focus light image Drawings for explaining.

6 is a view for explaining the relationship between the diameter of the mirroring light image and the distance between the focus light image in the optometry according to the present invention.

7A and 7B are diagrams for explaining a method of compensating measurement position error of an eye under the eyepiece according to an embodiment of the present invention, when the eye is located outside the focal length and inside the focal distance of the measurement light.

8 is a view for explaining a method for compensating measurement position error and a method for calculating a focus error graph "M _k " in an optometry according to an embodiment of the present invention.

Figure 9 is a flow chart of the corneal curvature measuring method according to an embodiment of the present invention.

Claims (5)

A mirror ring light source for irradiating ring-shaped measurement light to the cornea of the eye to be examined; A focus light source positioned at the center of the mirroring light source and irradiating the measurement light in the form of two dots to the cornea of the eye to be examined; An imaging optical system configured to detect a mirroring light image and a focus light image reflected from the cornea; And Computing the diameter (R) and the distance (F) of the focusing light image of each of the measuring light beam image and the measurement of the focusing light image, respectively, from the detected mirroring light image and the focusing light image An optometrist comprising a computational control device for measuring the curvature of the cornea of the eye under a light image. The method of claim 1, wherein the arithmetic and control device comprises the steps of: calculating a focus interval (D = R-F) during measurement from a diameter (R) of the miring light image and a distance (F) of the focus light image during the measurement; When the cornea of the eye to be examined is located at the focal length of the measurement light, the diameter of the mirroring light image and the distance of the focus light image are calculated, and the focus interval is calculated from the diameter of the mirroring light image and the distance of the focus light image, Deriving a relationship graph (L) of a diameter of the miring light image and the focus interval; Calculating a diameter (R ′) of a reference-based miring light image corresponding to the focus interval (D) in the measurement in the relationship graph (L); Calculating a focus error [Delta] R, [Delta] R = R-R 'from the diameter R of the miring light image during the measurement and the diameter R' of the miring light image during the reference; And determining whether the focus error ΔR is within an allowable range, and when the focus error ΔR is not within an allowable range, correcting the diameter R and the focus interval D of the measuring light image during the measurement. And measuring the corneal curvature of the eye under the measurement when the focus error (ΔR) is within the allowable range from the diameter (R) of the miring light image during the measurement. The diameter (R) of the measuring lighter image according to claim 2, wherein the correction of the diameter (R) of the measuring lighter image and the focusing interval (D) of the measuring light is measured in the relation graph (L). Calculating a reference time focus interval D ′ corresponding to the reference time; Deriving a focus error graph M _{d '} from the reference time focus interval D'; Calculating a diameter (R ″) of the corrected miring light image corresponding to the reference focal length (D ′) in the focus error graph M _{d ′} ; and the diameter of the measuring light image during measurement (R) and the focusing interval (D) at the measurement, respectively, the diameter (R ") and the reference focusing interval (D ') of the miring light image during correction are substituted to obtain the focus error (ΔR), and the position error An optometrist that determines whether is an acceptable range. Irradiating the corneal measurement light and the focus measurement light to the cornea of the eye, and detecting a miring light image and a focus light image reflected from the cornea; Computing the diameter (R) and the distance (F) of the focusing light image in the measurement, the measurement (R) and the diameter (R) of the mirroring light image in the measurement Calculating a focus interval (D, D = RF) during measurement from the distance (F) of the focus light image; When the cornea of the eye to be examined is located at the focal length of the measurement light, the diameter of the mirroring light image and the distance of the focus light image are calculated, and the focus interval is calculated from the diameter of the mirroring light image and the distance of the focus light image, Deriving a relationship graph (L) of a diameter of the miring light image and the focus interval; Calculating a diameter (R ') of a reference-based miring light image corresponding to the focus interval (D) during the measurement in the graph (L); Calculating a focus error [Delta] R, [Delta] R = R-R 'from the diameter R of the miring light image during the measurement and the diameter R' of the miring light image during the reference; Determining whether the focus error ΔR is within an allowable range; A correction step of correcting a diameter (R) and a focus interval (D) of the measuring light image when the focus error (ΔR) is not within an allowable range; And And measuring the corneal curvature of the eye under the measurement when the focus error ΔR is within an acceptable range. The method of claim 4, wherein the correcting comprises: calculating, in the graph (L), a reference visual focus interval (D ′) corresponding to the diameter (R) of the measuring light image; Deriving a focus error graph M _{d '} from the reference time focus interval D'; Calculating a diameter (R ″) of the corrected miring light image corresponding to the reference focal length (D ′) in the focus error graph M _{d ′} ; and the diameter of the measuring light image during measurement (R) and substituting the diameter R ″ and the reference focal length D ′ of the miring light image during correction into the focus interval D during measurement, respectively.

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