JPS6159134B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the refractive power of the eye, and in particular, it enables the measurement of the refractive power of the eye under conditions approximating situations in daily life, and also allows for centralized observation by the examiner. made possible.

Ophthalmic refractometers have been used for a long time to test human eye function and, more practically, to obtain data for adjusting eyeglasses, and various device structures have been proposed.

When measuring this eye refractive power, the diopter in the radial direction, that is, the spherical diopter, where the diopter becomes an extreme value, and the change in diopter that accompanies a change in the radial direction, that is, astigmatism and diopter, are at the extreme value. It is necessary to measure the direction of the radial line, that is, the astigmatism axis.

Previously, for example, US Pat. No. 3,883,233 and US Pat.
In the eye refractometer known as No. 1, the measurement direction along the radial line is changed by rotating the entire optical system or a part of the optical system around the optical axis, and the eye refractive power in the radial direction is changed. are measured continuously.

By the way, some well-known devices form a target image on which a subject's line of sight is fixed within a light-shielding housing that houses functional units for inspection and measurement. In that case,
Even if the apparent distance to the target image is optically corrected to a far distance such as 5 m or infinity, the subject will actually be looking into the target, resulting in so-called mechanical myopia. It is said that test and measurement results often differ from the natural state.

In other devices, the non-measuring eye is shielded to prevent the non-measuring eye from being distracted by peripheral vision and thus interfering with the fixation of the measuring eye. . However, since the human eye uses both eyes to work together to see things, there is a risk that there will be a difference between the visual acuity when one eye is looking and the visual acuity when both eyes are looking. It is desirable to perform the examination with binocular vision.

On the other hand, it is generally known in ophthalmological examinations that the illuminance of an image or object gazed at by a subject and the illuminance of the surroundings influence the examination results. Therefore, if you stare at an object in a dark place or test in a dark room, the test results may differ from those in natural brightness, so it is desirable to perform measurements in a room with normal brightness as much as possible.

On the other hand, the device usually gets in the way during measurement, making it impossible to observe whether the subject is gazing at the fixation target in the correct position. Because certain types of people and children tend to gaze in an unnatural manner or have a tendency to move their visual field, it is preferable to check the subject immediately before measurement, and also to find a location where it is easy to compare the measurement results with the image of the subject's eye. If it is displayed on the screen, it will be helpful for the examiner's judgment, and it has the advantage of not having to look here and there.

An object of the present invention is to provide a novel refractometer that meets the above needs.

Examples will be described below with reference to the drawings.

In FIG. 1, E is the eye to be examined, Ef is the fundus or retina, Ep is the pupil, and Ec is the cornea. Reference numeral 1 is a fixation target, which is placed away from the subject using a blinking light source, symbol, or picture. In this case, since no lens is placed between the eye E and the fixation target 1, mechanical myopia can be avoided, and when measuring long-distance refractive power, the patient should be placed at a distance of, for example, about 5 m from the eye to be examined. Support at a height equal to the optometry height.

2 is a dichroic mirror, which has the ability to reflect light with longer wavelengths than near infrared rays and transmit light with shorter wavelengths, as shown in Figure 13, which shows an example of the characteristics of transmittance T. Furthermore, since the fixation target 1 is provided obliquely to the line of sight of the subject's eye E, the subject can see the fixation target 1 through the mirror 2. The mirror 2 is also sized or constructed so that during the measurement both eyes can view the fixation target through this mirror of identical properties, thereby allowing binocular fixation. At this time, the subject naturally views the fixation target with binocular vision.

3 is an objective lens, arranged so that its optical axis is perpendicular, and a dichroic mirror 2 aligned with this optical axis.
Because they are arranged at a 45 degree angle, they are dichroic.
The virtual optical axis divided by the mirror 2 coincides with the lens optical axis. The mirror 2 and objective lens 3 constitute an objective optical system. Reference numeral 4 denotes a portion related to projection and detection of the measurement pattern, and details of this portion will be explained later with reference to FIG.

5 is the second dichroic mirror, which is aligned with the optical axis.
It is installed diagonally at an angle of 45 degrees, and has the ability to reflect infrared light and transmit shorter wavelength light, as shown in FIG. 14, an example of the characteristics of transmittance T. Note that the mirror 5 can be installed diagonally only during measurement instead of a quick-return mirror, and can be moved out of the optical path during alignment, but it is better to keep it fixed when considering the reproducibility of the arrangement. 6 is a beam splitter, 7
is a perforated lens, which has a hole 7a aligned with the optical axis as shown in FIG. 2, and the function of the hole will be described later.
Reference numeral 8 denotes an aiming plate, on which an aiming mark 8a (Fig. 3) is drawn. 9 is a relay lens, 10 is an image pickup tube or image sensor array such as a vidicon, 11
is a red light emitting diode that illuminates the eye to be examined, and is installed outside the housing.

The conjugate relationships of the above members are drawn with broken lines,
The anterior segment of the eye to be examined, for example, the corneal surface Ec and the aiming plate 8 are arranged to be conjugate with respect to the reflecting surface of the mirror 2, the objective lens 3 and the perforated lens 7, and the aiming plate 8 and the light receiving surface of the image pickup tube 10 are arranged to be conjugate with respect to the relay lens 9. do.
Therefore, the imaging tube 10 images the aiming mark superimposed on the anterior segment of the subject's eye.

Next, 12 is a light emitting diode that emits light with a wavelength longer than near-infrared, and 13 is a light shielding plate provided with a pinhole 13a. This pinhole 13a forms a mark for alignment, and here one pinhole 13a is provided on the optical axis, but a plurality of pinholes 13a may be provided symmetrically with the optical axis. The position of the light shielding plate 13 is determined as follows. When the positional relationship between the eye to be examined and the objective optical system is appropriate, and the cornea is regarded as a convex mirror,
The light beam emitted from the pinhole 13a is reflected by the reflective surface of the beam splitter 6, and is reflected by the second dichroic beam.
After passing through the mirror 5 and being converged by the objective lens 3, it is reflected by the surface of the dichroic mirror 2 and heads toward the cornea Ec. The light beam specularly reflected by the cornea Ec is then reflected by the surface of the dichroic mirror 3, is converged by the objective lens 1, and is then reflected by the dichroic mirror 5 and beam splitter 6.
Then, it passes through the hole 7a of the perforated lens and forms a pinhole image on the sight plate.
In other words, the pinhole 13a is made conjugate with respect to the beam splitter 6, the objective lens 3, and the dichroic mirror 2 at a position halfway between the corneal apex and the center of curvature of the corneal surface (which corresponds to the focal point of the convex mirror), and the aiming plate 8 is made conjugate with respect to the beam splitter 6, the objective lens 3, and the dichroic mirror 2. By disposing it on the rear focal plane of the lens 3, the light rays reflected by the cornea are converted into substantially parallel light, and the objective lens 3 forms an image on the aiming plate 8. Note that the anterior segment Ec image of the subject's eye is formed on the aiming plate with the combined refractive power of the objective lens 3 and the perforated lens 7.

With the above configuration, when the light-emitting diodes 11 and 12 are turned on, the invisible infrared and near-infrared light emitted from the light-emitting diode 11 illuminates the front part of the subject's eye, and the light beams scattered and reflected there are sent to the dichroic mirror. It is reflected by the surface of 2 and converged by the objective lens 3,
The near-infrared component passes through the second dichroic mirror 5, further passes through the beam splitter 6, and is once imaged on the aiming plate by the refractive power of the perforated lens 7.
Next, the relay lens 9 forms an image on the light receiving surface of the image pickup tube 10 . On the other hand, the infrared and near-infrared light beams emitted from the light-emitting diode 12 pass through the beam splitter 5, where only the near-infrared components are transmitted and head toward the subject's eye, but the dichroic mirror 2 reflects the near-infrared light. A pinhole image is formed on the light receiving surface of the image pickup tube 10 according to the optical action described above.

FIG. 4 shows a television receiver 14 which is electrically coupled to a television camera including an image pickup tube 10. As shown in FIG. A display screen such as a cathode ray tube of the image receptor projects an image of the front part of the subject's eye, an aiming mark image 8a', and an alignment mark image 13a'. However, in this case, the pupil of the eye to be examined and the aiming mark 8a' are misaligned, so the alignment between the eye to be examined and the objective optical system is broken, and the alignment mark image 13
Since a' is blurred, the operator can see that the distance between the eye to be examined and the objective optical system is inappropriate. On the other hand, although not shown in the drawing, the inspection instrument is equipped with a slide stage consisting of a left and right movable table slidably supported on a fixed base and a back and forth movable table supported on top of the slide stage.
The measurement main body is mounted on a telescoping support provided on a front-rear movable stage, and adjustments in the front-rear and horizontal directions are usually performed by operating a console connected to a slide stage. At that time, in order to centralize operations, there is a push-button release button on the terminal of the operation console.
If a switch is provided and pressed with the thumb, measurement can be started immediately after the positioning operation is completed, which is convenient. This is because alignment is extremely easy to go awry and remains the same for only a short period of time.

By adjusting the entire apparatus horizontally, vertically, and longitudinally relative to the eye to be examined, the state shown in FIG. 5 can be achieved. In Figure 5, aiming mark 8
a' and the pupil of the eye to be examined are arranged concentrically, and the alignment mark 13a' is located at the center of the aiming mark 8a', resulting in a clear image.

I would like to add here that if there is a positioning mark, it may seem that the aiming mark is not necessary, but the method using specular reflection is too sensitive, so it is necessary to make rough adjustments before positioning. It is often difficult to get the mark image within the screen, so it is convenient to have a mark for aiming.

Note that measurements are usually performed with one eye at a time.
To do this, the left/right movable base of the slide stage is moved so that the objective system faces the right or left side. At this time, for example, the position of the left/right movable base relative to the fixed base is detected using a micro switch, and the signal is also detected. ``OD'' or ``OS'' may also be displayed on the television receiver to indicate left or right eye. This is because the device often covers the front of the subject's face, making it difficult for the examiner to easily see the subject's eyes, and there is a risk of confusing the left and right eyes when remeasuring to confirm the measurement. Where there is
There is an advantage that this can be prevented.

The eye refractive power measurement unit will be explained below with reference to FIG. Explain why you chose the meridian of the book.

When the subject's eye has astigmatism, assuming that the change in diopter due to astigmatism in the meridian direction changes sinusoidally, the diopter can be expressed as a function of the angle in the meridian direction by the following equation.

D=Asin(2θ+α)+B (1) The variables D and θ represent diopter and meridian angle, respectively. The constants A, B, and α are the degree of astigmatism, the average diopter, and
Corresponds to the astigmatism axis direction. Since there are three unknowns in equation (1), if there are measured values in at least three meridian directions,
By applying equation (1), each value of the degree of astigmatism, average diopter, and astigmatism axis direction can be determined for any meridian direction. It goes without saying that by increasing the number of meridian directions to be measured, rather than limiting them to three, the accuracy can be improved by finding the above values in any three of them and averaging them with the values found in other combinations. do not have.

In Fig. 6, 20 is an infrared light emitting diode. 21 is a diaphragm plate having an opening 21 as shown in FIG.
It helps to separate the three beams of light. 22 is a condenser lens, 23 is a deflection prism, and the planar shape is the first
The shape shown in FIG. 5 and when viewed from the side is shown in FIG. 16, and has the effect of deflecting the light flux incident on each surface to the outside. Reference numeral 24 denotes a three-beam slit plate, and as shown in FIG. 10, slits 24a, 24b, and 24c are provided perpendicular to meridian lines that form 120 degrees with each other, and these slits form a measurement pattern.
Moreover, the deflection prism 23 has a three-beam slit plate 24.
Although they are placed close to each other, the order of placement may be reversed.
25 is a relay lens, 26 is a three-hole plate, and three openings 26a, 26b, 26c are arranged corresponding to each meridian as shown in FIG. 27 is another relay lens, which is integrated with members 25 and 26 and is movable in the optical axis direction.

28 is a relay lens, and 29 is a perforated mirror, which has three openings 29a, 29b, and 29c corresponding to each meridian as shown in FIG.

30 is a relay lens, 32 is a relay lens, 3
3 is an aperture diaphragm plate, and the aperture 3 is
3a. 34 is a relay lens, member 3
As a result of selecting the combined refractive power of lenses 25 and 27 to be the same as the combined refractive power of lenses 32 and 34, both units are combined, and a transfer means (not shown) is used. It is monotonically transferred in one direction only once during one measurement.

35 is the same three-beam slit plate as shown in Figure 10. 36a, 36b, and 36c are light guides such as optical fiber bundles or acrylic light guide rods, one end of each light guide is placed in contact with each slit opening of the three-beam slit plate, and the other end is placed in contact with each slit opening of the three-beam slit plate, and the other end is placed in contact with each slit opening of the three-beam slit plate. It is attached to a light-receiving element like this. With the above optical arrangement, the three-beam slits 24 and 35 are always kept conjugate with the point P with respect to the relay member.

Further, 38 is a position detecting means having a length measuring device such as an encoder, which constantly detects the axial position of the above-mentioned movable unit during measurement. Note that here the relay lens is moved as a movable unit, but
Alternatively, the three-beam slit plate may be moved in the axial direction together with the illumination section and the photometry section. The operation will be explained below, and the light rays showing the conjugate relationship in FIG. 6 are shown for the light beams emitted from arbitrary slits of the three-beam slit plate. When the light emitting diode 20 is turned on, the infrared light illuminates the aperture plate 21, and the luminous flux emitted from the aperture 21a is condensed onto the three-beam slit plate 24 by the condenser lens 22. At that time, due to the action of each surface of the deflection prism 23, each slit 24a, 24
The light beams passing through b and 24c are separated more effectively,
The light beams are converged by the relay lens 25, and each light beam is regulated by the apertures 26a, 26b, and 26c of the three-hole plate 26 to prevent the light beams from interfering with each other. then 3
After passing through the relay lens 27, the light beam forms an image, diverges, converges at the relay lens 28, passes through the apertures 29a, 29b, and 29c of the perforated mirror, and is reflected by the second dichroic mirror 5. , is imaged again, further diverged, subjected to a converging action by the objective lens 3, diverged by the dichroic mirror 2, and forms a measurement pattern image on a concave surface including point P and perpendicular to the optical axis. Now, assuming that the point P coincides with the fundus Ef, the light beam scattered and reflected by the fundus exits the subject's eye, travels back along its original optical path, is reflected by the dichroic mirror 2, and enters the objective lens 3. Once the image is formed,
Following the reflection from the second dichroic mirror 5, it is reflected from the mirror surface of the perforated mirror 29, and is imaged by the relay lens 30 behind the beam splitter 31.
Further, the image is formed on the three-beam slit plate 35 through the relay lens 32, aperture diaphragm plate 33, and relay lens 34, and the light beams that have passed through each slit 35a, 35b, and 35c pass through light guides 36a, 36b, and 36c, and are sent to the light receiving element. 37a, 37b, and 37c. At this time, if the point P coincides with the fundus, the image of the measurement pattern slit of the three-beam slit plate 24 will precisely match the slit of the detection three-beam slit plate and will be clearly formed, so the amount of light received will be Maximum value. However, when the point P is before or after the fundus Ef, the measurement pattern image formed on the detection three-beam slit is not only blurred, but also shifted in the meridian direction, so the amount of light received decreases. The reason why the image is shifted in the meridian direction is that the imaging position is formed by an off-axis light beam that is off the optical axis.
When the measurement starts, the movable units 25, 26, 2
When moving 7, 32, 33, and 34 from the initial position, the number of light receiving elements 37a, 37b, and 37c gradually increases, but if there is astigmatism, the three light receiving elements will not detect the peak value at the same time, but will gradually increase. The peak value will be taken.

FIG. 17 shows an example of an electric circuit, in which light receiving elements 37a, 3
7b and 37c are photo transistors. The output signals from each photo transistor 37a, 37b, 37c are amplified by amplifiers 45a, 45b, 45C, and output to peak detectors 46a, 46b, 4.
6c, and the peak value is detected. On the other hand, the position detector 38 constantly inputs the position detection signal to the arithmetic circuit 47 composed of a microprocessor, and the three sets of position signals at the time when the peak value is detected are applied to the above-mentioned equation (1). By doing so, you can obtain the information you are looking for. That is, D=Asin(2
In the θ+α)+B formula, the diopter (refractive power) D is determined from the position of the movable unit, and since the meridian direction θ is determined in advance, the average diopter (SPHERE)
A, degree of astigmatism (CYLINDER) B, and astigmatism axis (AXIS) α can be calculated. 59 holds the calculated results in a memory circuit.

On the other hand, a video signal corresponding to the image of the anterior segment of the subject's eye and the mark images for aiming and positioning by the image pickup tube 10 in FIG. 17 is output (x) from the television camera 48. As shown in FIG. 18, this signal consists of a video signal Vsig, a vertical synchronizing signal Vsync, and a horizontal synchronizing signal Hsync, and is input to the television receiver 14 through a mixing circuit 49. At this time, the video signal x is separated into a video signal and a synchronization signal by the synchronization separation circuit 50, and the data calculated by the arithmetic circuit 47 is combined by the OR gate 53 as a digital signal from the display control circuit 51 and character generator 52. This becomes a character signal y. This character signal is another one of the mixing circuits 49.
The video signal x and character signal y are mixed by a switching signal z from the display control circuit 51 to form a new mixed signal w, which is input to the television receiver 14, and its display is as shown in FIG. An image of the front part of the eye to be examined is displayed at the top of the screen, and measurement result data is displayed at the bottom. Note that the arrangement of numbers and letters can be arbitrarily selected.

FIG. 18 shows an example of the above-mentioned signal wavelength, where the horizontal axis represents time and the vertical axis represents voltage.
Video signal Vsig level is 0 to 1.0V, synchronization signal
The levels of Vsync and Hsync are about 0.2 to 0.3V, and if the video level of the character signal y is 0.5 to 1.0V, the background is black and white characters are displayed on the cathode ray tube. In addition, MC1545 (Motorola product) is a commercially available integrated circuit as mixed circuit 49.
etc., but it may also be composed of discrete elements.

Further, 54 in FIG. 17 is a printer, the customer card 55 is inserted into the printer, and the television receiver 14 is
When the user confirms the measurement result and releases the release button 54a, the measurement date and measurement result are printed in a blank space on the card 55.

Further, the photometry condition check function will be explained with reference to FIG. 40 is an imaging lens, 41 is an aperture diaphragm plate, and 42 is a light receiving element, and the light receiving element 42 is arranged close to the aperture diaphragm plate 41. and aperture plate 4
1 is configured to be conjugate with the pupil Ep of the eye to be examined with respect to the imaging lens 40, the relay lens 30, the aperture mirror 29, the second dichroic mirror, the objective lens 1, and the dichroic mirror 2, and the aperture is opened. The aperture is set to such an extent that the image on the pupil includes three light beams passing through the pupil. As a result, 3
The light beam split by the beam splitter 31 enters the light receiving element 42, and this photometric amount is determined by detecting individual differences in the reflectance of the fundus and adjusting the amplification level of the amplifiers 45a, 45b, and 45c. It can be used for adjustment, to check whether light is reflected on the cornea or to check for disturbance (meter 57), and the signal from the light receiving element 43 is amplified by the amplifier 56, and then compared to a predetermined signal by the comparator 5.
8, it is possible to display on the image receptor 14 that the subject blinked. This takes advantage of the fact that when the subject blinks, the measurement light is reflected by the eyelids, so the amount of light increases dramatically. The blinking is displayed on the image receptor in case the operator overlooks the subject's blinking.

The above embodiment can be modified in various ways. For example, the display surface of a display device such as a liquid crystal display that displays data from an arithmetic circuit may be arranged side by side with the aiming plate shown in FIG. 1, and both may be photographed at the same time. That's fine, but it has the advantage of being able to freely display character signals other than numbers by using the television's electrical processing circuit.

According to the present invention described above, the subject is allowed to see the fixation target naturally with binocular vision, and furthermore, the measurement is performed in a wavelength range that is invisible to the subject's eyes, so that unnecessary tension is not caused to the subject. Since it uses measurement light in a wavelength range different from that of indoor light, it has the effect of making it possible to focus on objects under normal indoor light. In addition, the eye to be examined can be observed on the display immediately before and after the measurement or during the measurement, and the measurement results are also displayed, which has the advantage of ease of use. That is, since the measurement results are displayed on the observation surface, it becomes easy to judge whether or not to take the measurement again based on the comparative observation of the state of the anterior segment of the subject's eye during measurement and the measurement results. Furthermore, by adding a light receiving section conjugate to the pupil of the eye to be examined, not only the presence or absence of blinking can be visually detected, but also the presence or absence of blinking can be automatically detected.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the embodiment. 2 and 3 are plan views of the constituent members of the embodiment, respectively. 4 and 5 are front views of the image receptor. FIG. 6 is a longitudinal sectional view of the embodiment. FIG. 7 to FIG. 12 are plan views of the constituent members of each embodiment. FIG. 13 and FIG. 14 are transmission characteristic diagrams of the constituent members of the embodiment, respectively. FIG. 15 is a plan view of the structural members of the embodiment, and FIG. 16 is a side view thereof. FIG. 17 is an electrical circuit diagram of the embodiment. FIG. 18 is an electrical signal waveform diagram. In the figure, 2 is a dichroic mirror, 3 is an objective lens, 5 is a second dichroic mirror, 1
0 is an image pickup tube, 14 is an image receiver, 24 is a three-beam slit plate, 37a, 37b, 37c are light receiving elements, 47
49 is a mixing circuit, and 50 is a synchronous separation circuit.

Claims (1)

[Scope of Claims] 1. A fixation unit that allows a subject to naturally see a fixation target with binocular vision via a wavelength-selective light splitter facing the subject; a measurement unit that measures refractive power information of the eye to be examined by irradiating a measuring beam of infrared light onto the fundus of the eye to be examined and receives the reflected light beam of the fundus; an imaging optical system for obtaining an image of the anterior segment of the subject's eye;
An eye refractometer comprising a display means for displaying the anterior segment of the eye to be examined by the imaging optical system and the calculated refractive power by the calculation unit. 2. A fixation section that allows the subject to naturally view the fixation target with binocular vision via a wavelength-selective light splitter facing the subject, and a fixation unit that allows the subject to view the fixation target naturally through a wavelength-selective light splitter facing the subject, and a measurement to the fundus of the subject's eye via the light splitter. a measurement unit that measures refractive power information of the eye to be examined by emitting a light beam and receiving a light beam reflected from the fundus; a calculation unit that is coupled to the measurement unit and calculates refractive power from the refractive power information; and an anterior segment of the eye to be examined. an imaging optical system for obtaining an image of
An eye refractometer comprising: a display means for displaying the anterior segment of the eye to be examined by the imaging optical system and the calculated refractive power by the calculation unit; and a light receiving part provided substantially conjugate with the pupil of the eye to be examined.