JPH0554327B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an objective type automatic eye refractometer having a fixation chart projection system that causes a subject's eye to have a foggy vision.

(Prior art) Conventionally, a target image for measurement is projected onto the fundus of the eye to be examined using invisible light, the in-focus state of this target image for measurement is detected photoelectrically, and based on this detection result, the image of the eye to be examined is determined. 2. Description of the Related Art An objective automatic eye refractive power measuring device for measuring refractive power is known.

In this objective automatic eye refractive power measuring device,
A fixation chart projection system is provided that projects a fixation chart using visible light in order to fix the line of sight of the eye to be examined in a predetermined direction, eliminate the accommodation power of the eye to be examined, and make the eye to be examined into a foggy vision state. . This fixation chart is located at a predetermined distance (for example, 3 diopters away) from the accommodation range of the eye to be examined, corresponding to the refractive power of the eye to be examined.

(Problems to be Solved by the Invention) However, in this conventional fixation chart projection system, the astigmatic power of the eye to be examined is not corrected, and it is difficult to accurately measure the astigmatic power of the eye to be examined. It had the following drawbacks.

In other words, in order to properly cause foggy vision in the subject's eye with astigmatic power, the fixation chart must be set so that it is located at a far point than the refractive power on the strong principal meridian. In this case, the amount of blur in the fixation chart becomes too large, making it difficult to stably gaze at the fixation chart, making it impossible to obtain highly accurate measurement results.

(Purpose of the Invention) The present invention was made with the aim of solving the problems of the prior art. It is an object of the present invention to provide an objective type automatic eye refractive power measurement device that can correct the degree of astigmatism and astigmatism axis of a fixation target based on the above, and measure refractive power with high precision.

(Means for Solving the Problems) The present invention provides astigmatism correction that corrects the degree of astigmatism of the eye to be examined based on the measurement results of the measurement system in a fixation chart projection system that projects a collimation index onto the fundus of the eye to be examined. An optical system is installed and the measurement system is used to perform precise measurements again.

(Function) According to the present invention, even in a subject with severe astigmatism, the astigmatism can be corrected using the astigmatism correcting optical system, and then re-measurement can be performed to correct the spherical power, astigmatic axis, and projection. The power can be measured accurately.

(Example) Examples of the eye refractive power measuring device according to the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing an optical system of an eye refractive power measuring device according to the present invention, and in this embodiment, an eye refractive power measuring device for both subjective and objective vision will be described. In this FIG. 1, 1 is a target image projection system, 2 is a target image projection system;
3 is an imaging optical system, 3 is a shared optical system shared by the target image projection system 1 and the imaging optical system 2, 4 is a chart projection system, 5 and 6 are aiming optical systems, 7 is an eye to be examined, and 8
is the anterior segment of the eye. The target image projection system 1 has a function of projecting target light onto the fundus 9 of the eye 7 to be examined via the shared optical system 3 to form a target image on the fundus 9. The target image projection system 1 is generally composed of a light emitting element 10, a condenser lens 11, an index plate 12, reflection prisms 13, 14, a relay lens 15, and a reflection prism 16. The light emitting element 10 emits infrared light with a center wavelength of 880 nm, and this infrared light is converted into a parallel light beam by the condenser lens 11 and has a function of illuminating the index plate 12. The indicator plate 12 has slits 12a to 12d as shown in an enlarged view in FIG.
is formed, and four deflection prisms 17 to 20 are attached to this index plate 12. The index plate 12 has a function of forming measurement target light by being illuminated with infrared light, and the index plate 12 has a function of forming measurement target light by being illuminated with infrared light.
Numerals 7 to 20 have the function of deflecting the target light in a direction perpendicular to the longitudinal direction of the slit.

The shared optical system 3 includes a half-moon diaphragm plate 21, a slit prism 22, an image rotator 23, and a beam splitter 25. The target light formed by the index plate 12 passes through the reflecting prisms 13 and 1.
4 and 16 and guided to the semilunar diaphragm plate 21, the semilunar holes 21a and 21a are shown enlarged in FIG.
through the reflective surface 22a of the slit prism 22.
reflected by the image rotator 23, objective lens 24, and beam splitter 25 to the subject's eye 7.
It is projected onto the fundus 9 through the pupil of the eye. The half-moon diaphragm plate 21 is arranged conjugately with the pupil position of the subject's eye 7, which is in an appropriate position, with respect to the objective lens 24, and directs the target light without causing reflected light harmful to measurement from the anterior segment of the subject's eye. It has a function of making the light enter the eye 7 to be examined. The image rotator 23 rotates the measurement target image formed on the fundus 9 by θ degrees in the meridian direction of the eye 9 by rotating it by θ/2 around the optical axis l of the shared optical system 3. FIG. 4 shows the planar shape of this image rotator 23. The beam splitter 25 is
Light with a wavelength within the range of 400nm to 700nm
75% reflection, 50% reflection of light with a wavelength in the range of 750nm to 820nm, and target light (wavelength
It has the property of transmitting 100% of light (880nm). Since this target light is invisible light, miosis due to projection of the target image is prevented.

The reflected light of the measurement target image projected on the fundus 9 is transmitted to the beam splitter 25 and the objective lens 2.
4, slit hole 22a of slit prism 22,
Aperture 26 formed in the center of aperture diaphragm plate 26
a (see FIG. 5), is guided to the imaging optical system 2 via a relay lens 27 and a reflecting prism 28. The aperture diaphragm plate 26 is arranged at a position conjugate with the pupil of the eye 7 to be examined, and has a function of guiding reflected light passing through the center of the pupil to the relay lens 27. The imaging optical system 2 includes a reflecting mirror 29, a fixed sunspot plate 30, a movable lens 31, a reflecting mirror 32, and a perforated mirror 3.
4 and an imaging lens 35, the fundus 9
It has a function of guiding the reflected light of the measurement target image formed in the image pickup device 36 to the photocathode 36a of the imaging device 36, and forming the measurement target image on the photocathode 36a. Here, the image rotator 23
When it is rotated by θ/2 degrees around the optical axis l, the measurement target image will be rotated by θ degrees in the rotation direction, but the reflected light of the measurement target image reflected at the fundus 9 will be reflected again in this direction. In order to pass through the image rotator 23, the measurement target image is rotated by θ degrees in the opposite direction to the rotation direction of the image rotator 23, and the measurement target image is displayed on the photocathode 36a of the imaging device 36 regardless of whether or not the image rotator 23 is rotated. An image is formed facing in a predetermined direction. Note that the fixed sunspot plate 30 is attached to the objective lens 2.
4 is provided at a position where the harmful light reflected at 4 is focused, and based on this, the reflected light harmful to the measurement is removed.

The chart projection system 4 includes a tungsten lamp 37
, color correction filter 38 , and condenser lens 39
, a chart disk 50 , and a collimator lens 41
, a moving lens 42 , and reflecting mirrors 43 and 44
, a relay lens 45 , a reflecting mirror 46 , and an objective lens 47 . The chart disc 50 is provided with a fixation chart board 51 and various charts for subjective optometry 52, and by rotating the chart disc 50, a desired chart board can be inserted into the optical path circle. ing. The chart board inserted into the optical path circle is illuminated by a tungsten lamp 37 via a condenser lens 39 and a color correction filter 38. The wavelength of the light emitted from the tungsten lamp 37 is selected by a color correction filter 38, and the color correction filter 38 transmits visible light having a wavelength of 400 nm to 700 nm. The fixation chart plate 51 is provided with a fixation chart 51a as shown in FIG. , 46, passes through an objective lens 47, and is guided to a beam splitter 48. This beam splitter 48 splits 75% of the visible wavelength light.
It has a reflective property, and the fixation chart light is
The beam is reflected by the beam splitter 48 toward the beam splitter 25, and
The light is reflected by and guided to the eye 7 to be examined. When performing objective measurement to automatically measure the refractive power of the eye 7 to be examined, the examinee fixates on the fixed finger chart 51a. When performing subjective measurement, for example, as shown in FIG. 7, a chart plate 52 for subjective optometry having a Landolt ring 52a and the like is inserted into the optical path. The chart disc 50 is provided with a large number of chart boards 52 for subjective optometry having charts of various patterns and sizes, and by rotating the chart disc 50, a desired chart board 52 can be selectively inserted into the optical path. death,
The eye is examined visually by the examiner. In FIG. 1, reference numeral 53 denotes a cylindrical lens optical system, which is arranged at a substantially conjugate position with the eyeglass wearing position of the eye 7 to be examined. This cylindrical lens optical system 23 will be described later. The movable lens 42 is disposed so as to be movable in the direction of its optical axis, and during objective measurement, it is set at a position that makes the eye 7 to be examined look like a fog, corresponding to the refractive power of the eye 7 to be examined, and to It is possible to carry out objective measurements with the accommodation force of the image 7 removed. In the case of subjective measurement, the movable lens 42 is moved in response to the test subject's response, and the refractive power of the test subject's eye can be measured from the amount of movement.

The aiming optical system 5 includes an infrared light source 54 that emits invisible infrared light with a center wavelength of 800 nm, a projection lens 55, and a perforated mirror 56. The light passes through a mirror 56 and a beam splitter 48, is reflected by a beam splitter 25, and is projected onto the cornea 7a. The optical axis l of the shared lens optical system 3 is the corneal vertex O
, the infrared light source 54 is placed at the corneal vertex O.
A bright spot image of the infrared light emitted from the eye is formed, and this is used to adjust the alignment of the optical system with respect to the eye 7 to be examined. The infrared light forming this bright point image is reflected at the corneal vertex at O, is reflected by the beam splitter 25, passes through the beam splitter 48, and is passed through the perforated mirror 56.
The direction is changed by and guided to the objective lens 57,
It is reflected by the perforated mirror 34 and passes through the imaging lens 3.
5, and is imaged on the photocathode 36a of the imaging device 36 as a bright spot image. Note that since this infrared light is also invisible light, miosis of the image 7 is prevented.

The aiming optical system 6 is roughly composed of an infrared light source 58 that emits infrared light with a wavelength of 700 nm, a diffuser plate 59', a scale plate 60', and a projection lens 61'. A circular hole 60'a is formed in the hole 60'a, and the infrared light passing through the circular hole 60'a becomes scale image projection light. The scale image projection light is reflected by the beam splitter 48 and the perforated mirror 56, guided to the objective lens 57, reflected by the perforated mirror 34, and guided to the imaging lens 35, and is imaged by the imaging lens 35. An image is formed on the photocathode 36a of the device 36 as a circular scale image. Note that the beam splitter 48 has a function of reflecting about 50% of this scale image.

The anterior segment 8 is illuminated by illumination lamps 62', 62', and the wavelength of the illumination light emitted from these illumination lamps 62', 62' is set to 800 nm. It is considered to be different from the wavelength. The reason for this will be described later. Since this illumination light is also invisible light, miosis of the subject's eye 7 due to the illumination light is prevented. The anterior eye illumination light reflected at the anterior eye segment 8 is reflected by the beam splitter 25, passes through the beam splitter 48, is reflected by the perforated mirrors 56 and 34, and is guided to the imaging lens 35. , this imaging lens 3
5, the reflection path of the bright spot image formed on the photocathode 36a of the imaging device 36 as an anterior segment image and reflected at the corneal vertex O is the same as the reflection path of the illumination light reflected at the anterior segment 8. The scale image projection path and the reflection path of the illumination light reflected at the anterior segment 8 have a common optical axis.

The imaging device 36 is connected to a television monitor 58, and 59 is its display surface. Display surface 59
Based on the video signal from the imaging device 36,
The image formed on the photocathode 36a is displayed. In FIG. 1, 60 is an anterior segment image, 62 is a circular scale image, 63 is a bright spot image, and 64 is a measurement target image. The measurer uses this display screen 59.
Anterior segment image 60 and circular scale image 62 displayed in
The alignment of the optical system can be adjusted while checking the positional relationship between the bright spot image 63 and the bright spot image 63.

When the target images 64 are in focus on the fundus 9, as shown in FIG. 9, the distance _l1 between the upper pair of target images 64a and the distance _l2 between the lower pair of target images 64b match. Yes, fundus 9
When the target image 64 is not in focus, the interval l ₁ and the interval l ₂ are different. For example, when the measurement target image is focused in front of the fundus 9, as shown in FIG. spacing l ₁
becomes smaller than the interval l ₂ and when the measurement target image is focused behind the fundus 9, the 11th
As shown in the figure, the interval l ₁ is larger than the interval l ₂ .
During objective measurement of refractive power, the index plate 12 is moved so that the distances l ₁ and l ₂ of the measurement target images 64 match, and the index plate 12 is moved until the distances l ₁ and l ₂ match. The eye refractive power is determined by the amount of movement when the lens 12 is moved. At this time, the movable lens 31 is driven so as to maintain a conjugate relationship with the index plate 12.

In the imaging optical system 2, a wavelength selection filter 65 is provided between the imaging lens 35 and the imaging device 36 so as to face the photocathode 36a of the imaging device 36. This wavelength selection filter 65 has wavelengths
A transparent glass plate that transmits both 800 nm light and 880 nm wavelength light is used, and as shown in Figure 11, the 880 nm wavelength light is transmitted in the half of the center where the target image is formed. Wavelength selective vapor deposited film 65 that allows light to pass through but blocks light with a wavelength of 800 nm
A is provided. This wavelength selection filter 65
According to the method, since the light forming the peripheral part of the anterior eye segment image 60 is blocked by the wavelength selective vapor deposited film 65a, the anterior eye segment image 60 is not projected onto the measurement target image 64 in an overlapping manner. Therefore, overlapping of the anterior segment image 60 and the measurement target image 64 can be prevented. In addition,
The perforated mirror 34 has a function of focusing the reflected light forming the anterior ocular segment image on one side of the photocathode 36a.

Next, a refractive power measurement circuit for objective measurement will be explained.

In Fig. 12, the refractive power measurement circuit is
66 and a signal detection circuit 67. The CPU 66 has the function of controlling a printer circuit 68, a drive circuit 69, a signal detection circuit 67, and a television monitor 58. The control mode can be switched between subjective measurement and objective measurement. The signal detection circuit 67 includes a target image signal detection circuit 71, a delay circuit 72, and a reference signal formation circuit 73.
The CPU 66 is configured to drive and control the drive circuit 69 based on the output output from the target image position detection circuit 75. . The drive circuit 69
2 and the movable lens 31 along the optical axis; a second drive control unit 69b for driving the image rotator 23 to rotate around the optical axis; It is composed of a third drive control section 69c for driving the moving lens 41 along the optical axis, and a fourth drive control section 69d for driving the cylindrical lens optical system 13 of the chart projection system 4, and the result of this drive is as follows. The information is fed back to the CPU 66, which performs calculations based on this information and outputs the measured value to the printer circuit 68.

Next, the function of the eye refractive power measuring device according to the present invention is as follows.
The following describes cases in which objective measurement and subjective measurement are performed with reference to the flowchart shown in FIG. It is assumed that an anterior segment image 60 and a measurement target image 64 are displayed on the display surface 59 at the same time.

When performing objective measurement, the CPU 66 first performs initial setting processing in step 100. Through this initial setting process, the index plate 12 is placed at the zero deopter position. The image rotator 23 is driven to rotate around the optical axis l, and as shown in FIG. Set the angle θ to be 45 degrees (this is called the 45 degree meridian). Furthermore, the movable lens 42 is moved so that the subject can visually recognize the fixed finger chart at the zero diopter position. Further, the cylindrical lens optical system 53 is set to a zero diopter. Next, the measurement mode changeover switch 70 is switched to the objective measurement mode, and the measurement mode switch is turned on. Then, in step 101, a process for determining whether the objective measurement mode switch is on is performed. When the objective measurement mode switch is on, in step 102, the distance l ₁ and l ₂ between the measurement target images is detected. Next, in step 103, it is determined whether this interval difference |l ₁ -l ₂ | is smaller than a predetermined value ε. The interval difference |l ₁ −l ₂ | is the predetermined value ε
If it is larger, in step 104, the index plate 12 is driven in a direction in which the interval difference |l ₁ -l ₂ | becomes smaller than the predetermined value ε. At this time, the movable lens 31 is also moved together with this, and the conjugate relationship between the index plate 12 and the photocathode 36a is maintained. Interval difference | l ₁ −
This step 102, 10 until l ₂ |<ε
Repeat 3,104. Along with this movement of the index plate 12, the third drive control section 69c moves the movable lens 42 to maintain the fog state for the subject. An anterior segment image 6 is displayed on the display surface of the display device 58.
0 and the measurement target image 64 are displayed, the examiner can observe under what conditions the measurement is being performed.

When the slit interval difference |l ₁ -l ₂ |<ε, the position of the measurement target image is read in step 105. Next, a process of reading the interval difference |l ₁ -l ₂ | value is performed (step 106). Based on the data obtained by reading the target image position (step 105) and reading the interval difference |l ₁ -l ₂ | value (step 106), the CPU 66 performs a refractive power calculation process (step 109). ). As a result, the refractive power in the 45-degree meridian direction is determined. Here, before performing the processing in step 109, the image rotator 23 is rotated every 30 degrees (step 108), the measurement target image is rotated every 60 degrees, the refractive power for the three meridians is determined, and the (Step 107). 1st
In Fig. 4, s' and s'' indicate the direction perpendicular to the longitudinal direction of the slit when the measurement target image is rotated 60 degrees.

Here, if the eye 9 to be examined has astigmatism, the measurement target image is detected separately as the image rotator 23 rotates. At that time, if the image rotator 23 is rotated around the optical axis, the refractive power D in the meridian angle θ direction is
It is expressed as the sum of the diopter value D _B at the movement stop position of the index plate 12 and the diopter value ΔD _B corresponding to the slit separation amount, and the relationship between the spherical power A, the astigmatic power B, and the astigmatic axis angle α is as follows. It is known that there is a relational expression that explains

Since D=A+Bcos(θ−α), the refractive powers D _B1 , D _B2 ,
If D〓 ₃ can be obtained by measurement, then based on the formula D〓 ₁ = A + Bcos2 (θ _1- 〓) D〓 ₂ = A + Bcos2 (θ _2- 〓) D〓 ₃ = A + Bcos2 (θ _3- 〓), The spherical power A, the astigmatic power B, and the astigmatic axis angle α can be obtained.

The main measurement is performed based on the calculation results of the spherical power A, the astigmatic power B, and the astigmatic axis angle α obtained in this way.

In this measurement, the meridian direction is divided into small sections, for example, 15 meridians. In this actual measurement, a cylindrical lens optical system 53 is used. This cylindrical lens optical system 53
is composed of a cylindrical lens 53a and a cylindrical lens 53b, and this pair of lenses 53a, 53
By rotating the lenses 53a and 53b integrally at an equal angle in the circumferential direction, the astigmatic axis is corrected, and by rotating the two lenses 53a and 53b at an equal angle in opposite directions, the astigmatic power is corrected. This cylindrical lens optical system 53 is driven and controlled based on the calculation results of the astigmatic power B and the astigmatic axis angle α, and is set so as to uniformly fixate the fixation chart of the subject (step 110).
Next, the third drive control section 69c moves the movable lens 42 to a position where the fog state is maintained for the subject (step 111). Through steps 110 and 111, the fixation chart is set in accordance with the refractive power of the subject's eye, and the subject can fixate the fixation chart uniformly and in an appropriate foggy state. Next, the image rotator 23 is rotated every 6 degrees, the measurement target image is rotated every 12 degrees, and the refractive powers D〓 ₁ to D〓 ₁₅ for the 15 meridians are measured (steps 112 to 115). ).
Based on the refractive powers D〓 ₁ to _{D〓 15} , the spherical power A, the astigmatic power B, and the astigmatic axis angle α are calculated by the least squares method, and the calculation results are displayed on the display screen (step 116). This measurement corrects astigmatism when the eye 7 to be examined has astigmatism, so the fixation chart is collimated to obtain accurate measurement results that do not affect the eye 7 to be examined which has astigmatism. become. Next, it is determined in step 117 whether or not to repeat the measurement, and if necessary, the measurements in steps 110 to 116 are performed again, and the final measured value is printed out (step 118).

Next, the case of performing subjective measurement will be explained.

In the case of subjective measurement, the movable lens 41 is moved in the optical axis direction of the chart projection system 4 based on the spherical power A of the eye 7 to be examined, and its moving position is set. Moreover, the astigmatic power B is corrected by the cylindrical lens optical system 53. In this state, the chart disc 50 is rotated and a desired optometry chart board 52 is inserted into the optical path. That is, in the subjective measurement, the chart board 52 for subjective optometry is visually recognized with the refractive power obtained in the objective measurement corrected.

The subjective measurement is performed by having the subject visually recognize the chart board 52 for subjective optometry. The examiner corrects the spherical power by driving the movable lens 42 and corrects the astigmatic axis and astigmatic power by driving the cylindrical lens optical system 13 according to the test subject's response. This drive amount is CPU66
and the measurement results are printed out as measured values in steps 120 and 121. During this subjective measurement, a measurement target image of invisible light is always projected onto the fundus of the eye to be examined, superimposed on the chart image for subjective ophthalmoscopy. At this time, the index plate 12 is always driven to a position corresponding to the corrected power in the chart projection system. At that time, the examiner can perform subjective measurements while observing the target image 64 displayed on the display surface 59 of the television monitor 58 as a visible image, so that the examinee can visually recognize the chart image in any condition. You can easily find out whether you have been tested while doing so.

In the above embodiments, an eye refractive power measuring device for both subjective and objective purposes has been described, but the present invention can also be applied to a subjective eye refractive power measuring device.

(Effects of the Invention) According to the present invention, even subjects with severe astigmatism can be made to gaze at the fixation chart in an appropriately stable state, and refractive power can be measured with high precision without accommodative force. can be done.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the optical system of the eye refractive power measuring device according to the present invention, FIG. 2 is an enlarged perspective view showing the detailed configuration of the index plate shown in FIG. 1, and FIG. FIG. 4 is an enlarged plan view showing the general shape of the image rotator shown in FIG. 1, and FIG. 5 is an enlarged plan view showing the shape of the half-moon diaphragm shown in FIG. 1. FIG. 6 is an enlarged plan view of the fixation chart shown in FIG. 1, and FIG. 7 is a plan view showing the shape of the chart for subjective optometry used in the eye refractive power measuring device according to the present invention. 8 to 10 are plan views showing the imaging state of the measurement target image shown in FIG. 1, and FIG. 11 is an enlarged plan view of the wavelength selection filter shown in FIG. 1. , FIG. 12 is a block diagram of a measuring circuit used in the eye refractive power measuring device according to the present invention, and FIG. 13 is a flowchart for explaining the measurement procedure of the refractive power measuring device for an ophthalmic instrument according to the present invention. FIG. 14 is an explanatory diagram for explaining the measurement procedure. 1... Target image projection system, 2... Imaging optical system, 3
... Common optical system, 4... Chart projection system, 5, 6... Aiming optical system, 7... Eye to be examined, 8... Anterior segment, 9... Fundus,
DESCRIPTION OF SYMBOLS 10... Light emitting element, 36... Imaging device, 36a... Photocathode, 58... Television monitor, 59... Display surface, 6
2'...Illumination lamp, 65...Wavelength selection filter, 6
5a,...Wavelength selective transmission section, 66...CPU.

Claims (1)

[Scope of Claims] 1. A measurement system that projects a measurement target image onto the fundus of the eye to be examined, photoelectrically detects this measurement target image, and measures the refractive power of the eye to be examined, and projects a fixation chart onto the eye to be examined. An objective automatic eye refractive power measurement device having a fixation chart projection system, wherein the fixation chart projection system is provided with an astigmatism correction optical system that corrects the degree of astigmatism of the eye to be examined based on the measurement results of the measurement system, An objective type automatic eye refractive power measuring device characterized by performing precise measurements again using a measuring optical system.