JP3539829B2 - Ophthalmic measurement device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ophthalmologic measurement apparatus that measures the refractive power of an eye to be examined.
[0002]
[Prior art]
When correcting the refractive error of the eye to be examined with a spectacle lens or a contact lens, a subjective test is performed to determine the prescription value. At the time of subjective examination, a method using measurement data of an eye refractive power measuring device for objectively measuring the refractive power of an eye to be inspected has been widely used. As an eye refractive power measurement device, a slit-shaped light beam is scanned and projected onto the fundus of the eye to be examined, and the light reflected from the fundus of the eye to be examined due to the projection of the slit light beam sandwiches the optical axis at a position substantially conjugate with the cornea to be examined. In order to obtain the refractive power of the eye to be inspected based on detection by two pairs of light receiving elements symmetrically arranged as described above. The measurement results of the apparatus assume that the refractive power of the eye is symmetric with respect to the center of the cornea so as to match the prescription value of the spectacle lens or the like, and S (spherical power), C (astigmatic power), A (astigmatic axis angle) Is calculated and output by the three parameters.
[0003]
[Problems to be solved by the invention]
However, the refractive power of the eye is not always symmetrical about the center of the cornea, and many eyes have irregular astigmatism. With an irregular astigmatic eye such as a keratoconus, the measurement results of S, C, and A obtained when the subject's eye looks at the center of the fixation target inside the device and when it looks at a position other than that are different. become. Therefore, conventional measurement data alone cannot provide sufficient refraction information for efficiently performing a subjective test.
[0004]
In recent years, corneal correction surgery, which corrects refractive errors by artificially changing the corneal curvature by excision of the corneal surface or the like, has been in the spotlight. In addition to the above, there is a demand for an apparatus that can determine the refractive power distribution at each part of the cornea. This is because the ultimate goal of the corneal correction surgery is how to bring the eye refractive power distribution closer to the emmetropic eye (or weakly myopic eye, weakly astigmatic eye).
[0005]
The present invention has been made in view of the above-mentioned prior art, and obtains the refractive power of the eye at a plurality of different radial corneal sites in one meridian direction and the refractive power of the eye by obtaining the eye refractive power at each of a number of meridional corneal sites. It is an object of the present invention to provide an ophthalmic apparatus capable of obtaining a distribution and knowing a refractive power state in detail.
[0006]
Another technique is to provide an ophthalmologic measuring apparatus which measures a corneal curvature distribution and a refractive power distribution with a single device, and makes it possible to know the relationship between the corneal curvature and the refractive power by associating both measurement data. Make it an issue.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by having the following configuration.
[0008]
(1) In an ophthalmologic measurement apparatus that measures the refractive power of an eye to be inspected, a slit projection optical system that scans the fundus of the eye with a slit light beam, a meridian direction corresponding to a slit direction of the slit light beam, and approximately the same as the cornea of the eye to be inspected. A detection optical system having a plurality of pairs of light receiving elements symmetrically arranged with an optical axis interposed therebetween at a conjugate position; and obtaining a refractive power of the eye to be examined changing in a meridian direction based on a phase difference signal output of each of the light receiving elements. And a refractive power calculating means.
[0009]
(2) The ophthalmologic measurement apparatus according to (1), further comprising: rotating means for rotating the slit light beam projected by the projection optical system and the light receiving element provided in the detection optical system in synchronization with each other about an optical axis; Control means for driving the means at a predetermined angle step, wherein the refractive power calculating means obtains a distribution of eye refractive power by obtaining a refractive power at a plurality of corneal sites for each of a number of meridian directions. I do.
[0010]
(3) The ophthalmologic measurement apparatus of (2) further comprises a display means for displaying the distribution of refractive power.
[0011]
(4) The display means of (3) is a means for displaying a graphic.
[0012]
(5) The ophthalmologic measurement apparatus according to (1) further sets the optical axis in a meridian direction not corresponding to the slit direction of the slit light beam by the projection optical system and at a position substantially conjugate with the cornea of the eye to be examined. At least a pair of second light receiving elements arranged symmetrically with respect to each other, center detecting means for detecting a corneal center or a visual axis center based on a phase difference signal output between the second light receiving elements, and a slit light beam And a refractive power calculating means for calculating a refractive power based on a phase difference signal between each of the pair of light receiving elements at a position corresponding to the slit direction and the detected center.
[0013]
(6) The ophthalmologic measurement apparatus according to (1) further includes a pupil diameter measuring unit that measures a pupil diameter of the eye to be inspected based on an output signal of a light receiving element of the detection optical system.
[0014]
(7) In the ophthalmologic measurement apparatus according to (1), the slit projection optical system has means for projecting slit light beams having at least two or more inclination angles, and the detection optical system has slit light beams of each inclination angle. And a plurality of pairs of light receiving elements arranged symmetrically with respect to the optical axis corresponding to the slit direction.
[0015]
(8) The ophthalmologic measurement apparatus of (1) further performs an index projecting means for projecting an index for measuring a corneal shape having a plurality of annular patterns on the cornea of the eye to be inspected, and detects and processes the projected index. A corneal shape measuring means for obtaining the shape of each area of the cornea, and a measuring mode switching means for switching between a mode for measuring a corneal shape and a mode for measuring an eye refractive power. .
[0016]
【Example】
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic layout diagram of an optical system of an apparatus according to an embodiment. The optical system is roughly classified into an eye refractive power measuring optical system, a fixation target optical system, a curvature measuring index projecting optical system, and a curvature measuring index detecting optical system.
[0017]
(Eye refractive power measuring optical system)
The eye refractive power measurement optical system 100 includes a slit projection optical system 1 and a slit image detection optical system 10. The slit projection optical system 1 has the following configuration. Reference numeral 2 denotes a slit illumination light source that emits light in the near infrared region, and 3 denotes a mirror. Reference numeral 4 denotes a cylindrical rotating sector which is rotated by a motor 5 at a constant speed in a constant direction. A number of slit openings 4a are provided on the side surface of the rotating sector-4. Reference numeral 6 denotes a projection lens, and the light source 2 is located at a position conjugate with the vicinity of the cornea of the subject's eye with respect to the projection lens 6. Reference numeral 7 denotes a limiting aperture, and reference numeral 8 denotes a beam splitter for making the main optical axis L1 facing the eye to be examined coaxial with the optical axis L2 of the slit projection optical system.
[0018]
The infrared light emitted from the light source 2 is reflected by the mirror 3 and illuminates the slit opening 4a of the rotating sector-4. The slit light beam scanned by the rotation of the rotating sector-4 is reflected by the beam splitter 8 after passing through the projection lens 6 and the limiting aperture 7. Thereafter, the light is transmitted through a beam splitter 9 which makes the optical axes of the fixation target optical system and the observation optical system coaxial, and is condensed near the cornea of the eye E, and then projected onto the fundus.
[0019]
The slit image detecting optical system 10 includes a light receiving lens 11 and a mirror 12 provided on the main optical axis L1, and a stop 13 and a light receiving unit 14 provided on the optical axis L3 reflected by the mirror 12. The aperture 13 is disposed at a focal position on the rear side of the light receiving lens 11 via the mirror 12 (that is, located at a position conjugate with the fundus of the eye to be examined of the normal eye). As shown in FIG. 2, the light receiving section 14 has eight light receiving elements 15a to 15h located at positions substantially conjugate to the cornea of the eye to be examined with respect to the light receiving lens 11, as shown in FIG. The light receiving elements 15a to 15f are located on a straight line passing through the center of the light receiving surface (optical axis L3), and the light receiving elements 15a and 15b, the light receiving elements 15c and 15d, and the light receiving elements 15e and 15f are respectively located at the center of the light receiving surface. It is provided so as to be symmetrical with respect to (ie, about the optical axis L3). The three pairs of light receiving elements are arranged at a distance so that the refractive power corresponding to each position of the cornea in the radial direction can be detected (in FIG. 2, it is shown as an equivalent size on the cornea). . On the other hand, the light receiving elements 15g and 15h are provided symmetrically on a straight line orthogonal to the light receiving elements 15a to 15h about the optical axis L3.
[0020]
In the eye refractive power measuring optical system 100 having such a configuration, the slit illumination light source 2 to the motor 5 of the slit projection optical system 1 have the optical axis L2 by the rotating mechanism 21 including the motor 20 and the gears. At the center, the light receiving section 14 rotates synchronously about the optical axis L3. The direction in which the light receiving elements 15a to 15f on the light receiving unit 14 are located is determined by the scanning direction of the slit light beam on the subject's eye projected by the slit projection optical system 1 (as if the slit light beam on the fundus occupies the length of the slit). (Scanning is performed in a direction perpendicular to the direction). In the apparatus of the embodiment, when the slit light beam is scanned by the slit opening 4a on the fundus of the subject's eye having no astigmatism, which corresponds to the direction orthogonal to the longitudinal direction of the slit received on the light receiving unit 14. Light receiving elements 15a to 15f are arranged as described above.
[0021]
(Fixation target optical system)
Reference numeral 30 denotes a fixation target optical system, 31 denotes a visible light source, 32 denotes a fixation target, and 33 denotes a light projecting lens. The light projecting lens 33 foggs the eye to be examined by moving in the optical axis direction. Numeral 34 is a beam splitter for making the optical axis of the observation optical system coaxial. The light source 31 illuminates the fixation target 32, and the light beam from the fixation target 32 passes through the light projecting lens 33 and the beam splitter 34, is reflected by the beam splitter 9, and travels toward the eye E to be examined. E fixes the fixation target 32.
[0022]
(Indicator projection optical system for curvature measurement)
The curvature measuring target projection optical system 25 has the following configuration. Reference numeral 26 denotes a conical placid plate having an opening in the center. The placid plate 26 is formed with a ring pattern having a large number of light transmitting portions and light shielding portions on a concentric circle centered on the optical axis L1. Reference numeral 27 denotes a plurality of illumination light sources such as LEDs. Illumination light emitted from the illumination light source 27 is reflected by a reflection plate 28 to illuminate the placido plate 26 almost uniformly from behind. The light beam of the ring pattern transmitted through the light transmitting portion of the placid plate 26 is projected on the cornea of the eye to be examined.
[0023]
(Indicator detection optical system for curvature measurement)
Reference numeral 35 denotes a curvature detection index detection optical system. The corneal reflected light flux of the ring pattern projected by the curvature measuring index projection optical system 25 is reflected by the beam splitter 9 and the beam splitter 34, and then is reflected by the photographing lens 37 onto the imaging element surface of the CCD camera 38. A corneal reflection image of a ring pattern is formed. The curvature detection index detection optical system also serves as an observation optical system, and an anterior eye image of the eye E to be inspected illuminated by an anterior eye illumination light source (not shown) passes through the beam splitters 9 and 34 and the photographing lens 37. Then, an image is formed on the image sensor surface of the CCD camera 38 and projected on the TV monitor 39.
[0024]
Next, the method for measuring the eye refractive power of the present invention will be described. In the eye refractive power measurement according to the present invention, first, the meridian center (or visual axis center) in the meridian direction where the light receiving elements 15a to 15f are located is obtained from the output signals of the light receiving elements 15g and 15h. The refractive power at the corresponding corneal site 15a to 15f is determined. In order to simplify the description, a pair of the light receiving elements 15a and 15b closest to the optical axis will be described as an example.
[0025]
Now, assume that the slit light beam is scanned at a constant speed by the slit projection optical system, and the signal output waveform when the slit image reflected from the fundus traverses each of the light receiving elements 15a, 15b, 15g, and 15h is as shown in FIG. This is the case where the subject's eye is in a hyperopic or myopic state and has astigmatism.
[0026]
Now, in the measurement of the eye refractive power by the phase difference method, when it is assumed that the refractive power is symmetric about the center of the cornea, the waveform signal from the light receiving element 15a in FIG. 3A and the waveform from the light receiving element 15b in FIG. The refractive power between the light receiving elements 15a and 15b can be obtained corresponding to the phase difference (time difference) with the signal. However, the refractive power is not always symmetric about the cornea center (or the visual axis center). Therefore, first, a method of obtaining the center of the light receiving elements 15a and 15b from the light voltage signals of the light receiving elements 15g and 15h located in the direction orthogonal to the light receiving elements 15a and 15b will be considered. Once the center is determined, the refractive power at each corneal site can be determined by obtaining the time difference between the corneal equivalent position of the light receiving element 15a or 15b and the corneal center (the visual axis center).
[0027]
Here, for the sake of simplicity, it is assumed that the rise time of the optical voltage signal waveform generated in each light receiving element in response to the incidence of light is detected (ta, tb, tg, and th in FIG. 3). The center of the light receiving elements 15a and 15b with respect to time t0 is
(Tg + th) / 2
Can be obtained by Therefore, if the time from the corneal site corresponding to the light receiving element 15a to the corneal center is Ta, and the time from the corneal center to the corneal site corresponding to the light receiving element 15b is Tb,
Ta = [(tg + th) / 2-ta]
Tb = [tb- (tg + th) / 2]
By making the times Ta and Tb correspond to the refractive power, the refractive power between the center of the cornea and a predetermined corneal part can be obtained.
[0028]
Next, a description will be given of a phase difference time at which an output signal from each light receiving element is binarized and detected. When a certain threshold level is set for a signal output from each light receiving element and binarization processing is performed, if there is a light amount difference between each light receiving element, an error may occur in the detection of the phase difference time. This is likely to occur when the translucent body of the eye is turbid, such as a cataract eye. For example, FIG. 4 is a diagram showing a state of signal waveforms from the corneal site corresponding to the light receiving element 15b when the corneal site corresponding to the light receiving element 15b is more turbid than the corneal site corresponding to the light receiving element 15a (FIG. In order to simplify the explanation, the light receiving timing is aligned). A waveform 65 indicates a signal waveform from the light receiving element 15a, and a waveform 66 indicates a signal waveform from the light receiving element 15b. The waveform amplitude of the light receiving element 15b is small due to turbidity. This analog waveform is shaped into a rectangular waveform at a certain threshold level 67 by a binarization process. However, when the amplitude changes, the rising times ta1 and tb1 from the reference time t0 when the rectangular waveform is shaped are obtained. , Δt. Therefore, when there is a light quantity difference between the respective light receiving elements, the time difference of Δt becomes an error when converted into refractive power.
[0029]
Therefore, in consideration of the case where there is a light quantity difference between the respective light receiving elements, the center in the meridian direction to be measured (the center of the cornea or the center of the visual axis) and the refractive power with respect to the center are half of the pulse width of the shaped pulse waveform. Take the time from the reference time at the location. This can eliminate the influence of the amplitude difference at each light receiving element position. That is, in FIG. 4, the times ta1, ta2, tb1, and tb2 from the reference time t0 are measured, and the time ta3 or tb3 to the center may be obtained. ta3 and tb3 are respectively
ta3 = ta1 + ta2 / 2
tb3 = tb1 + tb2 / 2
It becomes. This means that accurate time can be obtained even if the threshold levels in the binarization processing corresponding to the respective light receiving elements are different.
[0030]
FIG. 5 specifically shows such a time detection method for each light receiving element. (A) shows a digital waveform of a reference measurement pulse. In this case, among the light receiving elements 15a, 15b, 15g, and 15h, the timing at the first rising of the pulse waveform after the binarization processing is detected as the phase difference time. The standard is adopted. (B) to (e) show digital waveforms obtained from the four light receiving elements, and t_A3, T_B3, T_G3, T_H3Indicate the time from the reference time (rising edge of the measurement pulse) to the center of the pulse width. Therefore, when the direction of the light receiving elements 15a and 15b is the measurement meridian direction, the center (corneal center) is (t)_G3+ T_H3) / 2, and the time difference T at the position of the light receiving element 15a up to the calculated center._A, And the time difference T at the position of the light receiving element 15b from the center_BIs
T_A= (T_G3+ T_H3) / 2-t_A3
T_B= T_B3− (T_G3+ T_H3) / 2
Is required. Then, this time difference can be made to correspond to the refractive power with respect to the center in the meridian direction.
[0031]
Similarly, if the refractive power of the center and the light receiving elements 15c, 15d, 15e, and 15f is obtained, the refractive power at the cornea corresponding to the arrangement distance of each light receiving element can be obtained. When the slit projection optical system and the light receiving unit 14 are rotated by 180 degrees around the optical axis in synchronization with each other, the refractive power in all meridian directions (360 degrees) can be obtained.
[0032]
Further, by obtaining the refractive power at each site from the central part of the cornea to the peripheral part, it is possible to obtain the refractive power depending on the pupil diameter. Conversely, the pupil diameter of the eye to be examined at the time of measurement can be measured depending on whether each light receiving element in the measurement meridian direction has received the fundus reflection light. In the case of the embodiment, the measurement can be performed with an equivalent size on the cornea by the arrangement of the light receiving elements 15a to 15f shown in FIG.
[0033]
In the embodiment, three pairs of light receiving elements are arranged. However, if more than three pairs are arranged, more refractive power around the eyes can be obtained. Further, if the arrangement intervals of the light receiving elements are made closer, it is possible to obtain a refractive power at a finer portion.
[0034]
Next, the operation of the apparatus will be described with reference to the schematic block diagram of the signal processing system of FIG. First, the measurement mode is selected by the measurement mode switch 70. Here, continuous measurement of corneal curvature measurement and refractive power measurement will be described.
[0035]
The examiner performs alignment by moving the apparatus up, down, left and right and back and forth while observing the anterior eye image of the eye E illuminated by an illumination light source (not shown) with the TV monitor 39 (alignment is for alignment). A well-known one that projects an index onto the cornea so that the corneal reflection luminescent spot and the reticle have a predetermined relationship can be used. When the alignment is completed, a trigger signal is generated by a measurement start switch (not shown) to start the measurement.
[0036]
The continuous measurement starts with the corneal curvature measurement. The illumination light source 27 for curvature measurement is turned on for a predetermined time, and the ring pattern by the platinum plate 26 is projected on the cornea. The ring pattern image projected on the cornea is captured by the CCD camera 38 and then taken into the frame memory 71. The image captured by the frame memory 71 is subjected to edge detection processing by the image processing circuit 72, and the processed data is stored in the memory 73 via the control circuit 50.
[0037]
The control circuit 50 calculates the corneal curvature for each predetermined angle based on the stored edge detection position of the data. The calculation of the corneal curvature can be performed as follows. As shown in FIG. 7, the image height i of the light source P at the optical axis distance D and the height H from the cornea formed by the convex surface of the cornea on the two-dimensional detection surface by the lens L is represented by h. And the magnification of the optical system of the device is m, the corneal curvature radius R is
R = (2D / H) mh '
(For details of this calculation, refer to JP-A-7-124113). Further, for simplicity, the following calculation method may be adopted. The radius of curvature of the region where the j-th ring is projected on the cornea is Rj, the proportionality determined by the j-th ring height and the distance to the eye to be examined and the imaging magnification is Kj, and the image height on the imaging surface is hj Then, the above relational expression becomes
Rj = Kj · hj. Here, by measuring in advance a model eye having a plurality of known curvatures covering the measurement range, the proportional constant Kj can be obtained as a device-specific value. Then, the curvature distribution can be obtained in a very short time. It should be noted that, if the calculation processing of the curvature measurement in the continuous measurement mode is performed after the refractive power measurement is completed, the continuous measurement can be performed efficiently.
[0038]
Subsequently, a refractive power measurement is performed. Preliminary measurement of refractive power is performed by the same method as that of the conventional phase difference method. In this measurement, the projection lens 33 of the fixation target optical system is moved based on the refractive power obtained by the preliminary measurement, and the fixation target 32 and the fundus of the eye E to be examined are placed at conjugate positions. The fog is applied by the amount of diopter. From the slit projection optical system 1, a slit light beam restricted by the slit opening 4a enters the eye via the pupil and is projected on the fundus. The light flux of the slit image reflected by the fundus and passing through the pupil is condensed by the light receiving lens 11 of the slit image detecting optical system 10 and reaches the light receiving unit 14 via the aperture 13. Here, if the eye E to be examined is an emmetropic eye, a light voltage is generated in the light receiving elements 15a to 15h on the light receiving unit 14 at the same time when a light beam enters the eye. The image light moves so as to cross over the light receiving unit 14.
[0039]
With the movement of the light of the slit image on the light receiving section 14, a light voltage is output from each of the light receiving elements 15a to 15h (a time difference occurs in the light voltage). The output optical voltages are input to amplifiers 40a to 40h connected thereto, amplified, and further subjected to voltage level shift processing by level shift circuits 41a to 41h, respectively, and then binarized circuits 42a to 42h. It can be changed to a binarized pulse signal at a predetermined threshold level. After that, each pulse signal is input to the counter circuits 46a to 46h and the OR circuit 43, respectively. The OR circuit 43 sets the first rising edge in the binarization circuits 42a to 42h as the rising edge of the measurement pulse, and is input to the flip-flop 44 that follows. The flip-flop 44 includes a reference time (rising edge) as a start of measurement, and means a measurement time from completion of measurement of pulses from all light receiving elements to reception of an Rset signal output from the control circuit 50. The measurement pulse signal is output to the counter circuits 46a to 46d.
[0040]
When the pulse signals binarized by the binarization circuits 42a to 42h and the measurement pulse signal from the flip-flop 44 are input to the counter circuits 46a to 46h, the counter circuits 46a to 46h respectively correspond to the rising edge (= reference time) of the measurement pulse signal. And counts and holds the time until the pulse signal rises and the time of each pulse width. Referring to FIG. 5 as an example, the time until each pulse signal rises with respect to the reference time t0 is t t for each light receiving element._A1(In FIG. 5, t_A1= 0), t_B1, T_G1, T_H1It is. The pulse width time of the digital signal is t_A2, T_B2, T_G2, T_H2It is.
[0041]
The time held by each counter circuit is output by a call command signal (CSa to CSh) from the control circuit 50, and is input to the control circuit 50 via the data bus 47. The control circuit 50 determines the time (t) until the rise of each pulse signal with respect to the reference time in each light receiving element from each of the counter circuits 46a to 46h._A1, T_B1, T_G1, T_H1), Pulse width time (t_A2, T_B2, T_G2, T_H2), The time of the center of the cornea in the measurement meridian direction (scanning direction of the slit light beam) is determined by the above-described method, and then the time difference (phase difference) between three pairs of light receiving elements positioned in the measurement meridian direction with respect to the center ) Respectively.
[0042]
When a time difference at each corneal site in one meridian is obtained, this is converted into refractive power. FIG. 8 shows a relationship between the time difference detected by the phase difference method and the refractive power. This relationship can be obtained, for example, by sampling by using a model eye whose refractive power value is known in advance, and storing the data to obtain a refractive power value corresponding to the time difference.
[0043]
Next, the motor 20 is driven to rotate the slit illumination light source 2 to the motor 5 and the light receiving section 14 of the slit projection optical system 1 by 180 degrees around the optical axis at a predetermined angle step (for example, 1 degree). The refractive power at each rotational position is obtained based on the signal from each light receiving element. These refractive power measurements are repeated a plurality of times, and the results are subjected to predetermined processing (averaging, intermediate values, etc.) and stored. Further, by performing predetermined processing on the refractive power in each meridian direction, parameters S, C, and A, which are the same as the conventional parameters, are calculated.
[0044]
At this time, it is possible to know the pupil diameter of the subject's eye at the time of measurement, depending on whether each light receiving element in the measurement meridian direction has received the fundus reflection light, and when performing processing in consideration of this and the state of the refractive power distribution. Thus, more useful information can be provided at the time of subjective optometry.
[0045]
The measurement data of the eye refractive power distribution obtained as described above is displayed on the display 53. 9 and 10 show examples of the display. FIG. 9 shows a color map (or gray scale) of the refractive power distribution when viewed from the front. In the figure, the upper part where the color map is missing represents a portion where the light receiving element cannot receive the fundus reflection light due to eyelashes or the like and the refractive power distribution cannot be obtained. FIG. 10 is an example in which the distribution of the refractive power is displayed in an island three-dimensional manner.
[0046]
In the embodiment, three pairs of light receiving elements can obtain the refractive power corresponding to the cornea at three locations in the radial direction, and this is obtained by distributing the obtained refractive power between the corneal areas in accordance with the distance ( By performing the interpolation, the number of distribution bands can be increased, and the distribution state can be more easily grasped.
[0047]
It is also possible to convert the radius of curvature obtained by the corneal curvature measurement into corneal refractive power by a well-known method, and to display the distribution state graphically as shown in FIGS. 9 and 10. Further, when the corneal curvature distribution (corneal refractive power distribution: D = (n-1) / r, r = corneal curvature, n = equivalent refractive index of the cornea) and the eye refractive power distribution are simultaneously displayed in correspondence, Will be able to know the relationship between
[0048]
Furthermore, in order to make the eye refractive power distribution correspond to the corneal refractive power distribution, a columnar refractive power component can be extracted from the corneal refractive index, and compared with the astigmatic component of the eye refractive power, or the difference between the two can be displayed. Thereby, the state of residual astigmatism (difference between total astigmatism and corneal astigmatism of the subject's eye) can be known.
[0049]
By knowing the refraction state of the eye to be examined in detail in this manner, it is possible to provide data for appropriately performing the procedure even in corneal correction surgery for correcting a refractive error.
[0050]
In addition, since the pupil diameter of the subject's eye at the time of measurement is measured at the same time, this information can be used for eyeglass prescription and the like in subjective optometry.
[0051]
Although the present invention has been described based on the embodiments, the present invention can be variously modified. For example, as shown in FIG. 11, a plurality of slit openings 90a, 90b having orthogonal inclination angles are arranged in the rotating sector-4. As shown in FIG. 12, on the light receiving section 14, three pairs of light receiving elements 91a to 91f and three pairs of light receiving elements 91g to 91l are arranged on an orthogonal straight line so as to correspond to the scanning direction of the slit openings 90a and 90b. To place. In this way, the refractive power at the corneal site corresponding to the arrangement of the light receiving elements in the two meridian directions corresponding to the two orthogonal slit scans can be obtained. Therefore, if the slit projection system and the light receiving unit 14 are rotated by 90 degrees around the optical axis in synchronism, the refractive power in all meridian directions can be obtained, and the measurement time can be shortened as compared with the arrangement shown above. be able to. Further, if the number of inclination angles of the slit light beam is increased and the arrangement direction of the light receiving elements on the light receiving unit 14 is correspondingly increased, it is possible to obtain more refractive power in the meridian direction by reducing the rotation angle. .
[0052]
Further, when it is not necessary to make the meridian direction fine, it is possible to provide a device which can obtain a simple refractive power distribution according to the number of arrangement directions of the light receiving elements without providing a rotation mechanism.
[0053]
【The invention's effect】
As described above, according to the present invention, the eye refractive power at a plurality of corneal sites in the meridian direction and the eye refractive power distribution at each corneal site can be obtained, and the refractive power state can be known in detail. .
[0054]
Further, the corneal curvature distribution and the refractive power distribution are measured by one apparatus, and the relationship between the corneal curvature and the eye refractive power can be known by associating the measured data with each other.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic arrangement of an optical system of an apparatus according to an embodiment.
FIG. 2 is a diagram illustrating an arrangement of light receiving elements included in a light receiving unit.
FIG. 3 is a diagram showing an example of signal output waveforms from four light receiving elements with respect to a reference time t0.
FIG. 4 is a diagram showing an example of a signal waveform from both the corneal site corresponding to the light receiving element 15b and the corneal site corresponding to the light receiving element 15b when turbidity is large.
FIG. 5 is a diagram showing a detection method of the binarization processing of the present invention for each light receiving element.
FIG. 6 is a schematic block diagram of a signal processing system of the apparatus according to the embodiment.
FIG. 7 is a diagram illustrating a method of calculating a corneal curvature.
FIG. 8 is a diagram illustrating a relationship between a time difference detected by a phase difference method and a refractive power.
FIG. 9 is a diagram showing a display example of measurement data of an eye refractive power distribution.
FIG. 10 is a diagram showing another display example of measurement data of the eye refractive power distribution.
FIG. 11 is a diagram showing an example of the arrangement of slit openings when measurement is performed in two meridian directions.
FIG. 12 is a diagram illustrating an example of the arrangement of light receiving elements when measurement is performed in two meridian directions.
[Explanation of symbols]
1 Slit projection optical system
4a slit opening
10. Slit detection optical system
15a-15h light receiving element
46a-46h counter circuit
50 control circuit
100 Eye refractive power measuring optical system

Claims (8)

In an ophthalmologic measurement apparatus that measures the refractive power of the eye to be examined, a slit projection optical system that scans the fundus of the eye to be examined with a slit light beam, and a position that is substantially conjugate with the cornea of the eye to be examined in a meridian direction corresponding to a slit direction of the slit light beam. A detection optical system having a plurality of pairs of light receiving elements arranged symmetrically with respect to the optical axis, and a refractive power calculation for obtaining a refractive power of the eye to be examined changing in a meridian direction based on a phase difference signal output of each of the light receiving elements Means. The ophthalmologic measuring apparatus according to claim 1, further comprising: a rotating unit configured to rotate the slit light beam projected by the projection optical system and a light receiving element included in the detection optical system in synchronization with each other about an optical axis; Ophthalmic measurement, wherein the refractive power calculating means obtains a refractive power distribution at a plurality of corneal sites in a plurality of meridian directions to obtain an eye refractive power distribution. apparatus. The ophthalmologic measurement apparatus according to claim 2, further comprising a display unit for displaying a distribution of refractive power. 4. An ophthalmologic measurement apparatus according to claim 3, wherein the display means is a means for displaying a graphic. The opthalmologic measurement apparatus according to claim 1, further comprising: a mirror that reflects reflected light from the fundus of the eye to be examined in a meridian direction that does not correspond to a slit direction of the slit light beam by the projection optical system and at a position substantially conjugate to the cornea to be examined. At least a pair of second light receiving elements, center detecting means for detecting a corneal center or a visual axis center based on a phase difference signal output between the second light receiving elements, and a slit direction of the slit light beam. And a refractive power calculating means for calculating a refractive power based on a phase difference signal between each of the pair of light receiving elements at a position corresponding to the detected center and the detected center. 2. The ophthalmologic measurement apparatus according to claim 1, further comprising a pupil diameter measurement unit that measures a pupil diameter of the eye to be inspected based on an output signal of a light receiving element of the detection optical system. 2. The ophthalmologic measuring apparatus according to claim 1, wherein the slit projection optical system has means for projecting a slit light beam having at least two or more inclination angles, and the detection optical system has a slit direction of the slit light beam at each inclination angle. An ophthalmologic measuring apparatus comprising a plurality of pairs of light receiving elements arranged symmetrically with respect to the optical axis in correspondence with the above. An ophthalmologic measuring apparatus according to claim 1, further comprising: an index projecting means for projecting a corneal shape measurement index having a plurality of annular patterns onto the cornea of the eye to be inspected; An ophthalmologic measuring apparatus comprising: a corneal shape measuring means for obtaining a shape of a region; and a measuring mode switching means for switching between a mode for measuring a corneal shape and a mode for measuring an eye refractive power. .

Images