JP3046062B2 - Eye refractive power measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eye-refractive-power measuring apparatus, and more particularly to a photorefractive-type eye-refractive-power measuring apparatus.

[Prior art] Conventionally, as an eye refractive power measuring device, a fundus of a subject's eye is illuminated with a strobe light, a state of a light beam in a pupil of the subject's eye is photographed by a camera, and the eye refractive power of the subject's eye is measured from the result. There is a so-called photorefractive eye refractive power measuring device.

However, in this device, the measurement range is limited,
It has a disadvantage that accurate measurement cannot be performed.

For this reason, the present applicant disclosed in Japanese Patent Application Laid-Open No. 2-191428 that a light source image was projected on the fundus of the subject's eye, a light beam reflected from the fundus from the light source was blocked by an edge-shaped light shielding member, and the blocked light beam was received. An eye-refractive-power measuring device that receives an element and measures the eye-refractive power based on the light amount distribution state of the light flux has been proposed, and has made it possible to measure the eye-refractive power instantaneously with high precision.

[Problems to be Solved by the Invention] However, in the above-described apparatus, when calculating the eye refractive power based on the measurement result, the pupil diameter of the eye to be examined must be measured, and the calculation must be performed based on the pupil diameter. Must
In addition to the measurement of the light amount distribution, a configuration for measuring the pupil diameter of the eye to be examined is required.

Means for Solving the Problems The present invention has been made to solve the problems of the prior art, and has as its object to propose an apparatus that does not need to measure the pupil diameter of the subject's eye each time it is measured. A light source that emits a light beam, and a projection system diaphragm that is disposed at a position substantially conjugate with the pupil of the eye to be examined and has a translucent portion smaller than the pupil diameter of the eye to be inspected, and forms a light source image on the fundus of the eye to be inspected through the translucent portion. A projection system for projecting, a light receiving system that guides a light beam from the fundus on a light receiving element arranged at a position substantially conjugate with the pupil of the eye to be inspected, and a part of the received light beam that is arranged in the light path of the light receiving system and blocks light And a calculator for calculating the eye refractive power of the eye to be inspected based on the distribution of the amount of light of the light beam projected on the light receiving element.

According to the present invention, a projection stop having a light-transmitting portion smaller than that of a general human pupil system is arranged at a position conjugate with the pupil of the eye in the projection system for projecting a light source image on the fundus of the eye. By doing so, the pupil of the eye to be inspected always has a light flux having a constant aperture diameter corresponding to the size of the translucent image of the projection stop projected on the pupil of the eye to be inspected, regardless of the pupil diameter of the eye to be inspected. It is not necessary to specifically measure the size of the pupil diameter of the eye to be inspected unlike the conventional apparatus.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

As described above, in the earlier application, the diopter value of the eye to be inspected is measured based on the light intensity distribution received by the light receiving element. However, if the slope of the light intensity distribution is defined as digital f / f ₀ , the eye to be inspected relative to the reference diopter value D ₀ The deviation ΔD of the diopter value of It is known that there is a relationship L: light source size u: pupil diameter

Therefore, in the eye refractive power measuring device proposed above, the pupil diameter u is measured. However, as described below,
In the present embodiment, an aperture is provided to simulate the pupil diameter u required for measurement, and the measurement of the pupil diameter is omitted.

In FIG. 1, reference numeral 1 denotes a fundus 7 of an eye 3 to be measured,
Is a light-receiving system for receiving the measurement light beam reflected by the fundus 7;
Is a projection system for measuring a corneal shape that projects an index light beam onto the eye 3 to be inspected. The projection system 1 for measuring the refractive power of the eye and the light receiving system 2 are arranged to face the eye 3 to be inspected. The optical axis is shared with the projection system 1 for measuring eye refractive power, and the optical axis is arranged around the optical axis.

The eye refractive power measurement projection system 1 includes a light source 4, a half mirror 10, a mirror 11, and a beam splitter 13, and a condenser lens 14 is disposed between the light source 4 and the half mirror 10.
A relay lens between the half mirror 10 and the mirror 11
15. A projection system stop 16 is provided, and a projection system objective lens 17 is provided between the mirror 11 and the beam splitter 13. The projection system stop 16 and the pupil 6 are a projection system objective lens.
The position is substantially conjugate with respect to 17.

The above-described projection system 1 for measuring an eye refractive power converts the light beam from the light source 4 into a condenser lens 14, a half mirror 10, and a relay lens.
The light source 4 is guided to the subject's eye 3 via the projection system aperture 16, mirror 11, projection system objective lens 17, and beam splitter 13, and forms an image of the light source 4 on the fundus 7 through the pupil 6. The eye refractive power measuring projection system 1 is configured so that the image of the light source 4 is focused on the fundus 7 when the eye refractive power of the eye 3 to be examined is a reference diopter value (reference refractive power). Have been.

The light receiving system 2 includes a light receiving system objective lens 18, a relay lens
Light beams from the fundus 7 are projected through the beam splitter 13 onto the light receiving element 9.

The light receiving element 9 is an area CCD, an image pickup tube, or the like,
The light receiving surface 9a of the light receiving element 9 is disposed at a position substantially conjugate with the pupil 6 of the eye 3 to be inspected.

In the optical path of the light receiving system 2, a light receiving system stop 21 can be disposed at a position conjugate with the projection system stop 16 with respect to the beam splitter 13. Further, an edge-shaped member 12 for blocking a part of the light beam is disposed at a position substantially conjugate with the light source 4 with respect to the beam splitter 13. In this embodiment, an edge-shaped light blocking member 12 for blocking one side of the light beam with the light receiving system optical axis O as a boundary is disposed.

The corneal shape measuring projection system 5 includes a ring-shaped emitting source 22 arranged so as to share the optical axis O, and a condensing lens 23 for projecting a light beam from the ring-shaped light emitting source 22 onto the cornea as a parallel light beam. Further, a front face illumination light source 24 is disposed outside the ring-shaped light emitting source 22, and the index light flux emitted from the ring-shaped light emitting source 22 is transmitted through the condenser lens 23 to be parallel and ring-shaped. Is projected onto the cornea as a reference light beam.

It should be noted that a plurality of light emitting sources may be prepared concentrically for the ring-shaped light emitting source 22.

Next, the wavelength of the light source 4 and the wavelength of the ring-shaped light source 22 are made different. For example, if the wavelength of the light source 4 is 750 nm to 850 nm,
When the wavelength of the ring-shaped light emitting source 22 is 850 nm or more, and the light receiving system stop 21 of the two stops is disposed, it is formed of an optical film, and only the light beam from the light source 4 is formed at the center and the periphery is formed. Is designed to transmit only the light beam from the ring-shaped light source 22 and the light from the anterior segment illumination light source 24. At this time,
The central portion may transmit anterior segment illumination light. Further, at least the central portion of the projection system stop 16 of the two stops, that is, the diameter of the measurement light beam transmitting portion is made smaller than the pupil diameter in consideration of individual differences.

Further, with respect to the half mirror 10, a fixation target 26 for fixing the eye to be inspected and a lens 25 are arranged.

An arithmetic unit 27 is connected to the light receiving element 9.
Reference numeral 27 denotes an image signal from the light receiving element 9, which is further stored to obtain a light amount distribution based on the image signal, further calculates a diopter value, a deformation amount of the index light beam, and outputs the result to the display 28. It has become. Further, the arithmetic unit 27 can output the image of the light receiving element 9 to the display unit 27 as it is.

At this time, the calculation may be performed after performing the measurement for a plurality of times. When displaying on the display, if there is an error or if there is data with low reliability due to eyelashes etc., the value considered to be the most reliable among multiple times may be displayed good. Although not shown, it is also possible to output this data to the outside, and in this case, it is also possible to output all data.

Incidentally, if the portion enclosed by the two-dot chain line in FIG. 1 is configured to be movable together, it is possible to enlarge the measurement range and make the fixation target 26 look far or cloudy with the eye to be examined. Furthermore, it is also possible to fix the measurement light source 4 and the fixation target 26, place a moving lens on the projection side, and move the moving lens and the edge-shaped light shielding member. Alternatively, the edge-shaped light shielding member and the light source may be fixed, and only the fixation target may move the movable lens.

 Hereinafter, the operation will be described.

 First, the alignment operation will be described.

The ring-shaped light emitting source 22 and the frontal face illumination light source 24 are turned on, and the subject gazes at the fixation target 26 with the light source 4 turned off.

At the time of the alignment work, the image of the light receiving element 9 is displayed on the display 28 as it is so that the examiner can observe the state of the alignment.

At this time, the edge-shaped light shielding member 12 and the light source 4 are set at a predetermined reference position in order to make the eye to be viewed far or cloudy.
For example, it is placed at zero diopter and measured. The edge-shaped light-shielding member 12, the light source 4, and the fixation target 26 or only the fixation target 26 are moved to the position of the result, and the measurement is performed in a state where the eye to be inspected is far vision or cloudy vision. When each moving member is measured at a predetermined reference position, only a specific meridian may be measured.

When measuring at the reference position, the difference from the reference position may be too large to detect. In such a case, it is determined whether or not detection is possible by moving again by moving a predetermined amount or a predetermined number of times. If it is not possible, an error or measurement range is exceeded, and output to the display 28 or an external device (such as a printer) as necessary.

In addition, the measurement at the reference position is performed in a state where the length of the light source L is increased, and the movable part is moved according to the measurement result.
It is also possible to perform the measurement in a state where the length is shortened.
For example, four LEDs are prepared, and at the time of measurement at the reference position or when detection was not possible at the reference position, four LEDs are lit even after movement, and detection and measurement are performed. Turn on two and measure. This is because the length of the light source L and the measurement range are related, but the sensitivity of the tilt is also related.

Since the light source changes when the length of the light source L changes, the brightness of the light source itself can be automatically adjusted so that the light amount at the pupil position does not change.

In a state where the light source 4 is turned off, if there is the light receiving system stop 21, there is no light beam transmitted through the central portion, and the central portion becomes dark. In addition, since the light from the ring-shaped light source 22 passes through the light-receiving system stop 21, a dark portion 29 at the center and a ring-shaped bright portion 30 are displayed on the display 28 as shown in FIG. . Thus,
The alignment is completed by positioning the subject so that the dark portion 29 and the ring-shaped bright portion 30 are concentric, for example, by positioning the subject with a chin rest, forehead rest, and moving the main body.

Alternatively, the light source 4 may be turned on, the ring-shaped light emitting source 22 may be turned off, and a bright spot on the cornea formed by the light source 4 may be used so that the bright spot becomes the center of the stop.

Further, an alignment reference target may be separately provided so as to form an image on the light receiving element and projected. When the light source 4 is turned on only at the time of measurement, a bright spot projection system for alignment for projecting on the cornea is separately provided. At this time, at the time of measurement, the alignment reference target projection light and the alignment bright spot projection light source are turned off.

 When the alignment is completed, the measurement starts.

 First, the measurement of the eye refractive power will be described.

Only the light source 4 is turned on, and the light beam for measurement is projected on the fundus 7 of the subject's eye. As described above, since the projection system stop 16 is located at a position conjugate with the pupil 6, the measurement light beam is projected onto the fundus 7 of the subject's eye in the same state as when the measurement light beam is stopped down to a light beam having a pupil diameter by the iris.

The light beam reflected by the fundus 7 of the subject's eye passes through the beam splitter 13 and the objective lens 18, reaches the light shielding member 12 without being disturbed by the light receiving system diaphragm 21, and a part of the light beam is shielded by the light shielding member 12. And is projected onto the light receiving element 9.

In the present embodiment, half of the optical axis is shielded from light, but for example, the shape and arrangement of the light source are adjusted in accordance with the measurement meridian,
Various shapes of the light shielding member are also conceivable.

When the edge-shaped light-shielding member is movable, since the edge-shaped light-shielding member moves, the anterior ocular segment observation light beam is affected. The size should not be given. For example, as shown in FIGS. 4 (A), 4 (B) and 4 (C), the optical film 35 is formed, and only the anterior segment observation light is transmitted, and the measurement light is not transmitted. The edge part (the part without hatching) transmits only the measurement light. When the anterior eye observation light is turned off at the time of measurement, the anterior eye observation light may be transmitted.

The video signal received by the light receiving element 9 is input to the arithmetic unit 27, and the arithmetic unit 27 calculates the light amount distribution and the slope Δf / f ₀ (described above) of the light amount distribution.

Further, the size L of the light source is a value uniquely determined by the shape of the light source, and the pupil diameter u is also simulated by the projection system stop 16 or the light reception system stop 21. These values L and u are input to the arithmetic unit 27 as constants in advance as known values in the device configuration.

Note that, in the case of a configuration that only measures the refractive power, the light-receiving system diaphragm 21 may not be provided. In this case, the projection system aperture
Since the light-receiving element 9 and the light-receiving element 9 have a substantially conjugate positional relationship, only the signal at the position corresponding to the projection-side stop among the video signals received by the light-receiving element 9 needs to be calculated.

Even if there is a light receiving system stop 21, the projection system stop 16 and the light receiving system stop
Since 21 is placed in a substantially conjugate positional relationship, it is similarly necessary to calculate only a signal at a substantially conjugate position on the light receiving element. This makes it possible to calculate without detecting the pupil position / diameter from the bright spot detection.

At this time, the light receiving element 9 may be one-dimensional or two-dimensional. Further, it is also possible to store the data in a memory and calculate after performing image processing such as bright spot elimination and cooling of the influence of eyelashes. Since the bright spot removal is not performed, for example, the size of the bright spot does not usually vary greatly depending on the person, a predetermined range may be determined in advance, and the calculation may be performed without using the data in the range. When performing bright spot detection, it is sufficient to search for a certain range of only the position on the light receiving element corresponding to the projection system stop or the light reception system stop. By doing so, the processing time is shortened.

The arithmetic unit 27 calculates the gradient of the light amount distribution (Δ
f / f ₀ ) is calculated, the deviation ΔD of the diopter value is directly calculated from the gradient from the above equation (1), and the diopter value D is calculated by the following equation.

D = D ₀ + ΔD (3) The calculation result is displayed on the display 28 or recorded and displayed by a recording means such as a printer (not shown).

Next, measurement of the shape of the cornea will be described with reference to FIG.

When measuring the shape of the cornea, the light source 4 is turned off and the ring-shaped light source 22 is turned on. The ring-shaped index light beam from the ring-shaped light source 22 is projected onto the cornea via the condenser lens 23.
The target light beam projected on the cornea is reflected by the cornea to form a virtual image inside the cornea. This virtual image is projected on the light receiving element 9 by the light receiving system 2. Therefore, the shape of the target light beam projected on the cornea can be seen from the signal from the light receiving element 9.

If the shape of the cornea is a perfect spherical surface, the shape of the index light beam at the light receiving element 9 is a perfect circle, but if the shape of the cornea is not a perfect circle, it becomes an ellipse 31 as shown in FIG.

This elliptical shape can be calculated by sequentially calculating the coordinates of the pixel of the light receiving element 9 receiving the index light beam in the arithmetic unit 27.

Here the reference coordinate system on the light receiving element 9 and X _O -X _O, the long axis direction of the calculated obtained was ellipse X _K axis, the minor axis direction and Y _K axis.

The radius S _XK of the major axis (X _K axis) of the ellipse 31 corresponds to the radius of curvature R ₁ of the weak main line of the cornea C, and the S _{YK of} the short axis (Y _K axis) is the radius of curvature of the strong main line. corresponds to R _2, the angle of the major axis theta _K1 and minor angle theta _K2 are each axial angle theta ₁ of Tsuyonushi _meridian, corresponding to the axis angle theta ₂ of the weak main meridian.

The general formula of the ellipse 31 in the X _K -Y _K coordinate system is A _X ² + B _Y ² + C _XY = 1 (4) Is represented as

The radius S _{K of the} ellipse 31 is represented by r as the radius of the cornea, h as the radius of a perfect circle as a reference, and β as the overall magnification of the optical system.
Then, since S _K = Y × β Y = h × r / 2 (6), S _XK and S _YK are obtained from equations (4) and (5), and the weak principal diameter is obtained from equation (6). The radius of curvature r ₁ of the line is The radius of curvature r ₂ of the strong main diameter wire is similarly Can be obtained as

Also, the axis angle of the strong main diameter line is obtained as θ ₁ = θ _K2 , and the axis angle of the weak main diameter line is θ ₂ = θ _K1 .

After the calculation is completed, the calculation result is displayed on the display 28 and output by a printer or the like as appropriate.

In the above measurement, the light source 4 and the ring-shaped light source 22 were individually turned on, and the eye refractive power and the corneal shape were measured individually. However, the reflected light beam of the light source 4 and the reflected light beam of the ring-shaped light source 22 were measured. When the light receiving system stop 21 is disposed, the light source 4 and the ring-shaped light source 22 are simultaneously separated because they are completely separated by the light receiving system stop 21 and concentrically separated and projected on the light receiving element 9. By turning on the light, the corneal shape can be simultaneously calculated from the light amount distribution from the central light receiving portion, the slope of the light amount distribution, and the coordinates of the light receiving pixels around the central light receiving portion.

FIG. 5 shows another embodiment in which a fixation target system 33 for measuring the corneal shape is provided separately from the one for measuring the refractive power. The position may be adjusted according to the refractive power of the subject. Further, in this embodiment, an anterior ocular segment observation system 34 is provided separately from the light receiving system 2.

[Effects of the Invention] As described above, according to the present invention, the pupil diameter of the eye to be inspected necessary for measuring the eye refractive power can be simulated in advance and treated as a known value. The calculation can be omitted, the measurement procedure can be simplified, the calculation unit can be simplified,
The arithmetic processing time can be reduced, and the optical axis of the eye refractive power measurement system and the corneal shape measurement system are shared. Therefore, an excellent effect that the configuration of the apparatus can be significantly simplified can be exhibited. .

[Brief description of the drawings]

FIG. 1 is a basic schematic diagram of the present invention, FIG. 2 is an explanatory view showing a projected state on a light receiving element, FIG. 3 is a view showing a shape of a ring-shaped index light beam projected on the light receiving element, FIG. (A) (B)
(C) is a diagram showing the shape of the light shielding member, and FIG. 5 is a basic schematic diagram showing another embodiment. 1 is a projection system for measuring an eye refractive power, 2 is a light receiving system, 3 is an eye to be examined,
4 is a light source, 5 is a projection system for measuring a corneal shape, 9 is a light receiving element,
Reference numeral 12 denotes a light blocking member, 16 denotes a projection system stop, 21 denotes a light reception system stop, and 27 denotes a calculator.

Claims (4)

(57) [Claims] 1. A light source for emitting a measurement light beam, and a projection system stop disposed at a position substantially conjugate with the pupil of the eye to be inspected and having a translucent portion smaller than the pupil diameter of the eye to be inspected. A projection system for projecting a light source image on the fundus of the eye to be examined, a light receiving system for guiding a light beam from the fundus on a light receiving element arranged substantially conjugate with the pupil of the eye to be examined, and a light receiving beam arranged in the light path of the light receiving system An edge-shaped light-shielding member for shielding a part of the light-receiving element, and a calculator for calculating an eye refractive power of the eye to be inspected based on a light amount distribution state of a light beam projected on the light receiving element. Eye refractive power measurement device. 2. An eye refracting power according to claim 1, wherein a light-receiving stop having a light-transmitting portion for measuring a light beam smaller than the pupil diameter of the eye to be examined is arranged at a position substantially conjugate with the pupil of the eye to be examined in an optical path of the light-receiving system. measuring device. 3. An anterior ocular segment illumination system for projecting illumination light toward an eye to be examined is provided. The wavelength of a measurement light beam and the wavelength of the illumination light beam are made different. Blocking the light of the wavelength of the illumination light beam and transmitting the light of the wavelength of the measurement light beam,
3. The eye refractive power measurement according to claim 2, wherein a portion other than the light transmitting portion is configured to block light having a wavelength of the measurement light beam and transmit at least a portion of light having a wavelength of the illumination light beam. apparatus. 4. A target light beam projection system for projecting a ring-shaped target light beam toward the cornea of the eye to be inspected is provided, wherein the wavelength of the measurement light beam and the wavelength of the target light beam are made different, and the transmittance of the light-receiving system diaphragm is changed. The light unit blocks light having the wavelength of the target light beam and transmits light having the wavelength of the measurement light beam, and blocks the light having the wavelength of the measurement light beam and excludes at least one light having the wavelength of the target light beam in portions other than the light transmitting portion. 3. The eye-refractive-power measuring device according to claim 2, wherein the eye-refractive-power measuring device is configured to be partially transmitted.