JPH0554773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an eye refractive power measuring device for objectively and automatically measuring the refractive power of the eye.

[Conventional technology]

Conventionally, various so-called objective eye refractometers that objectively measure the refractive power of the eye have been known.
In this type of device, shortening the measurement time has become an important issue because temporal changes in eye refractive power tend to cause measurement errors.

In order to solve this problem, we developed an eye that does not use a movable optical member during measurement, but instead separates the light beam reflected from the fundus and makes it enter the optical position detection element, and photoelectrically detects the image interval to speed up the measurement. A refractometer has already been developed and disclosed, for example, in Japanese Patent Application Laid-Open No. 161031/1983.

In this type of device, when separating the fundus reflected light flux and making it incident on the optical position detecting element, two indices P ₁ and P ₂ are placed on the optical position detecting element 13 as shown in FIG.
a and measure the image interval D. Here, when the image is displaced due to the refractive error of the subject's eye, the image interval D can be detected from 0 to the maximum, and the change from the length l of the optical position detection element 13a can be detected, and the images P ₁ and P ₂ can be detected. Although the amount of displacement is 1/2, it is actually shorter than 1/2 because both ends and the center of the optical position detection element 13a cannot be detected from the viewpoint of signal processing. Therefore, the amount of image displacement that can be detected is a little less than 1/2 of the length of the optical position detection element 13a, and if a short optical position detection element is used, the measuring range of the eye refractive power cannot be widened, and the position detection may be difficult. This causes problems such as difficulty in setting the resolution finely.

In order to improve the above-mentioned problem, by detecting how one index image is displaced with respect to the reference position of the optical position detecting element, the position of the reflected light beam from the fundus can be detected over a wide range using an optical position detecting element of a certain length. An eye refractive power measuring device is disclosed in Japanese Patent Laid-Open No. 60-210236, in which the measurement range can be expanded and the resolution of position detection can be finely set.

[Problem that the invention seeks to solve]

Comparing the two here, the former has problems such as it is difficult to widen the measurement range and make the resolution finer, but in terms of eye optics, the human eye is divided into smaller parts and measured. Because of this, detailed information about astigmatism can be obtained. The latter is the opposite. The refractive power distribution of the human eye falls within the range of mild hyperopia to moderate myopia for most people, and this is a range that can be adequately covered by the former eye refractive power measuring device. If these people have no disease other than refractive error, they can obtain sufficient visual acuity through correction with glasses or the like. On the other hand, there are a small number of people with extremely severe myopia or farsightedness, which are distributed over a wide range of areas, and many of whom have insufficient corrected visual acuity. In this case, a device for measuring the latter eye refractive power becomes useful. However, switching between the two is generally difficult.

[Means for solving problems]

The purpose of the present invention is to provide an eye refractive power measuring device that can measure the majority of people using a detailed method, and automatically measure a small number of people who cannot be measured using a method that prioritizes the measurement range. will be provided. This objective is achieved by adding a variable diaphragm mechanism and selecting the diaphragm mechanism to easily switch between the two methods described above.

〔Example〕

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated in detail based on the Example of illustration.

FIG. 1 shows an embodiment of the present invention,
A projection optical system is arranged on an optical axis 01 coaxial with the axis of the eye E to be examined, and a light receiving optical system is arranged on an optical axis 02 orthogonal to the optical axis 01. The projection optical system includes a light source 1 such as an infrared ray, a condenser lens 2, and a condenser lens 2 arranged sequentially from the opposite side of the eye E to be examined.
It is composed of a projection mask 3, a relay lens 4, an aperture plate 5, a perforated mirror 6, and an objective lens 7. As shown in FIG. 2, the projection mask 3 is
It has linear slits 3a, 3b, and 3c that are at an angle of 120 degrees to each other and oriented in a direction perpendicular to three predetermined meridians, and these slits 3
A to 3c serve as measurement indicators projected onto the fundus of the eye to be examined. In addition, the diaphragm aperture plate 5 has an optical axis 01 as an aperture.
It has only a circular opening at the top. perforated mirror 6
The light-receiving optical system placed on the reflection side of the
Hole, aperture plate 8, fixed 6-hole aperture 9, relay lens 10, prism 11, cylindrical lens 12
a, 12b, 12c, one-dimensional optical position detection element 1
3a, 13b, and 13c. As shown in FIG. 3, the movable three-hole aperture plate 8 has one fan-shaped opening 8a, 8b, 8c in each meridian direction perpendicular to the slits 3a, 3b, 3c. Further, the fixed six-hole aperture plate 9 has two fan-shaped openings 9a, 9a',
9b, 9b', 9c, and 9c'. As shown in FIG.
Consisting of 1a', 11b, 11b', 11c, 11c',
These prisms are arranged to cover the openings 9a to 9c', respectively. Therefore, the openings 9a to 9
The light beams passing through c' are refracted in each meridian direction and separated from each other.

In order to receive this separated light flux, the cylindrical lenses 12a to 12c and the optical position detection elements 13a to 13c are arranged in pairs and aligned with each meridian with the optical axis 02 as the center, as shown in FIG. has been done. That is, each cylindrical lens 12
a to 12c are arranged so that their generatrix directions match the respective meridian directions, and when a one-dimensional photodiode array is used, the optical position detection elements 13a to 13c are arranged so that the direction in which the photodiodes are arranged coincides with each meridian direction. has been done.

Regarding the optical positional relationship between these members, if the eye E to be examined is an emmetropic eye, the focal plane F of the objective lens 7 is conjugate with the fundus Er with respect to the objective lens 7. Further, the projection mass 3 is conjugate with the focal plane F with respect to the relay lens 4, and each light receiving surface of the optical position detection elements 13a to 13c is connected to the relay lens 10.
is conjugate with the focal plane F with respect to Further, the diaphragm aperture plate 5 is configured to adjust the pupil Ep of the eye E with respect to the objective lens 7.
The luminous flux that projects the chart is regulated to pass through the center of the pupil Fp. Fixed 6
The aperture plate 9 is also conjugate with the pupil Ep with respect to the objective lens 7, and out of the light flux reflected by the fundus Er, the pupil
The light beams from 6 places around the Ep are 6-hole aperture plate 9
passes through each opening 9a to 9c'. The cylindrical lenses 12a to 12c can condense and guide the light from the slit portions to the respective optical position detection elements 13a to 13c in a direction perpendicular to the longitudinal direction of the slit, that is, in the slit width direction. appears to be optically wider.

Next, to explain the operation of this embodiment, the infrared light emitted from the light source 1 is transmitted to the aperture plate 5 by the condenser lens 2.
The projection mask 3 is illuminated in such a manner that it converges on the projection mask 3.
The light beams emitted from the slits 3a to 3c of the projection mask 3 are subjected to an imaging action by the relay lens 4, and after being narrowed down by the diaphragm aperture plate 5, a chart image is formed on the focal plane F, and then a chart image is formed on the focal plane F. It is collimated by the lens 7, enters the fundus Er from the center of the pupil Ep, and forms a chart image. The light beam reflected by the fundus Er is imaged by the objective lens 7, then reflected by the perforated mirror 6, and passes through the apertures of the diaphragm plates 8 and 9. Then, it is subjected to an imaging action by the relay lens 10, deflected in each imaging direction by the prism 11, and cylindrical lenses 12a to 1
2c, each optical position detection element 13a~
The images are respectively formed on 13c.

When the eye E to be examined is an emmetropic eye, the chart image includes the focal plane F, the fundus Er, and the optical position detection elements 13a to 13.
A clear image is formed on c.

If the eye E to be examined is not an emmetropic eye, the chart image once formed on the focal plane F will be formed before or after the fundus Er depending on the condition of the eye E, so a blurred chart image will appear on the fundus Er. is projected. The angle of the light flux passing through each aperture of the diaphragm plates 8 and 9 and entering the prism 11 via the relay lens 10 changes depending on the diopter.

Therefore, the image position on each of the optical position detection elements 13a to 13c moves from the image position in the case of an emmetropic eye according to the diopter, and the eye refractive power for each meridian can be determined from the amount of movement. I can do it.

Next, signal processing of the output signals of the optical position detection elements 13a to 13c will be explained with reference to FIG. In FIG. 8, the above-mentioned optical position detection elements 13a to 13a, each consisting of a one-dimensional photodiode array, for example, are shown.
13c stores the brightness of the projected chart image. The channel selection signal S1 outputted from the microcomputer 14 via the interface circuit 15 causes the analog multiplexer 1 to
6 is switched to the a channel, and the read signal Sa is applied to the optical position detection element 13a via the drive circuit 17a. As a result, the analog signal S2 corresponding to brightness stored in the optical position detection element 13a is extracted, and after being amplified by the amplifier 18a, it is passed through the analog multiplexer 16 to the sample hold circuit 19 and the analog/digital converter 2.
0, it is converted into a digital signal S3. and,
The data is stored in a read/write memory (RAM) 22 via an interface circuit 15 and a microcomputer 14. Similarly, optical position detection elements 13b, 1
3c information channel selection signal S1 and readout signal
Sb and Sc are sequentially switched, analog-to-digital conversion is performed, and the data is stored in the read/write memory 22.

In FIG. 8, 23 is a programmable read-only memory (PROM), and based on this information, the microcomputer 14 calculates which position on the optical position detection elements 13a to 13c is the brightest.

That is, the programmable read-only memory 23
includes optical position detection elements 13 for each channel a to c.
Reference positions corresponding to normal eyes a to 13c are stored. Note that 21 is a numeric display.

Here, the operation of the movable aperture plate 8 shown in FIG. 1 and the relationship between the optical position detection element 13a and the chart image will be explained.

The movable 3-hole aperture plate 8 can be moved in the direction of the arrow, and is fixed at position 8 in the figure when inserted into the optical path.
It overlaps concentrically with the aperture diaphragm plate 9, and is located at a position 8' in the figure when moved away from the optical path. When measuring the eye E, the movable diaphragm plate 8 is first inserted into the optical path and placed over the fixed 6-hole diaphragm plate 9. Each opening of the fixed 6-hole diaphragm plate 9 is opened by the movable 3-hole diaphragm plate 8.
9b' and 9c' are blocked, and the light flux emitted from the fundus Er of the subject's eye is blocked in one of the meridian directions, and
In this direction, the light beam 03 passes through, and the light beam 04 is blocked, and one chart image _P1 is formed on the optical position detection element 13a as shown in FIG.

When the subject's eye E has a refractive error, the position of the chart image shifts from the reference position of each of the optical position detection elements 13a to 13c depending on the degree of the abnormality, so the effect of the signal processing circuit shown in FIG. The image position is detected and stored in the read/write memory 22.

The microcomputer 14 reads out the previously stored reference positions of each channel a to c and information on the currently measured position, and calculates the amount of deviation and direction of each imaging position using the reference position as the origin. Further, the programmable read-only memory 23 stores in advance a mathematical formula for converting this amount of deviation into a diopter, and based on this information, the microcomputer 14 calculates the diopter for each meridian.

At this time, if the diopters of all meridians are within a predetermined range, the movable three-hole diaphragm plate 8 is moved out of the optical path as shown in FIG. 1, and the eye to be examined is measured again.
This time, in the meridian a direction, the apertures 9a and 9a' are opened, and the light beams 03 and 94 reach the optical position detection element 13a,
Two chart images are formed as shown in FIG.
This imaging position is detected by the action of the signal processing circuit system shown in FIG. 8, and is stored in the read/write memory 22. Further, the programmable read-only memory 23 stores in advance a mathematical formula for converting the distance between these two imaging positions into diopter, and based on this information, the microcomputer 14 calculates the diopter for each meridian.

To summarize the above, in Figure 10, the two chart images A and B are movable for the subject's eye in the range from both ends of the optical position detection element until the two images in the center touch, depending on the degree of refractive error of the subject's eye. The aperture 8 is removed and measurement is performed with two light beams in each measurement meridian direction, and the diopter is determined from the interval between them. On the other hand, the two images overlap,
For eyes to be examined that intersect, one light beam is measured in each meridian direction with the movable diaphragm plate 8 inserted in the optical path, and the diopter is determined based on the amount of deviation from the reference point at that position. In this way, it becomes possible to obtain the diopter over a wide range that cannot be obtained using the method shown in FIG.

Control of the moving in and out of the movable diaphragm plate 8 is performed by the microcomputer 14, and at the same time, the formula for calculating the diopter is also changed.

In this way, by measuring the diopters in the three radial directions, the degree of astigmatism (SPH), astigmatic axis angle (CLY), and spherical diopter (AX) are calculated, and the values are displayed on the numerical display 21. .

FIG. 9 is a flowchart illustrating the above procedure.

In the above embodiment, the measurement range was expanded using one movable diaphragm, but in addition to the fixed diaphragm and the movable diaphragm shown in Figure 3, a movable diaphragm waiting to open in the opposite direction to that shown in Figure 3 was added. , by switching both apertures,
Even with the light beam on the opposite side, measurement can be performed over the entire length of the optical position detection element, making it possible to obtain an even wider measurement range. For example, in the intermediate range of -10 to +10D, measurements are made with only a fixed diaphragm, in the range of high myopia of -10 to -30D, the first movable diaphragm is inserted, and in the range of high hyperopia of +10 to +30D, the second movable diaphragm is inserted. Insert a movable aperture and measure.

In this embodiment, the measurement using one light beam for each meridian was performed first, and then the measurement using two light beams was performed, but the same effect can be obtained by performing the reverse procedure.

In addition, in the above embodiment, the aperture was changed by calculating the diopter, but it was determined from the output signal waveform of the optical position detection element that the two light beams were not separated and were interfering, and the measurement using two light beams was changed from the measurement using one light beam. You may also switch to measurement. In this case, the time required is shorter than the time required to calculate the diopter. Note that interference in the output signal waveform can be determined from changes in signal height, base width, half-width, slope, etc.

By the way, in the above-mentioned embodiment, two light beams and one light beam were switched for all three meridian directions to be measured.
Of course, it is also possible to switch between two light beams and one light beam only partially in the first or second meridian direction among the three meridian directions.

Furthermore, in the above embodiments, the number of passbands for the received light flux was changed mechanically, but the diaphragm plate was constructed of liquid crystal.
It is also possible to electrically change the number of transparent regions.

〔Effect of the invention〕

As explained above, according to the eye refractive power measuring device according to the present invention, there is no moving member at all, it is possible to measure eye refractive power at high speed, and the entire range of the optical position detection element can be effectively used. Since it can be used, the measurement range can be widened and the resolution of position detection can be improved. Moreover, the movable diaphragm only serves as a shield, and the actual optical diaphragm is a fixed diaphragm, so the movable part does not affect accuracy.

[Brief explanation of drawings]

1 to 9 show an embodiment of the eye refractive power measuring device according to the present invention, FIG. 1 is an optical layout diagram of the embodiment of the present invention, and FIGS. 2 to 6 are front views of the constituent members. Figure 7 is a diagram of the relationship between the chart image and the optical position detection element, Figure 8 is a block circuit diagram of the signal processing circuit system, Figure 9 is a flowchart of the measurement procedure, and Figure 1 is a diagram of the relationship between the chart image and the optical position detection element.
Figure 0 is a diagram of the relationship between the projection chart and the optical position detection element in a conventional eye refractive power measurement device. In the figure, 1 is a light source, 2 is a condensing lens, 3 is a projection mask, 4 is a relay lens, and 5 is an aperture. Aperture plate, 6
1 is a perforated mirror, 7 is an objective lens, 8 is a movable 3-hole diaphragm plate, 9 is a fixed 6-hole diaphragm plate, 10 is a relay lens, 11 is a prism, 12a to 12c are cylindrical lenses, 13a to 13c are optical position detection elements , 14 is a microcomputer, 22 is a read line memory, and 23 is a programmable read-only memory.

Claims (1)

[Claims] 1. A projection optical system that projects an index onto the fundus of the eye to be examined;
It has a light receiving optical system that receives the light flux reflected from the fundus, and an aperture that separates the projected light flux and the received light flux on a plane approximately conjugate with the pupil of the eye to be examined. An apparatus for measuring eye refractive power, characterized in that the diaphragm is capable of selecting the number of pass zones for the received light beam in the measurement meridian direction. 2. The eye refractive power measuring device according to claim 1, wherein the diaphragm is composed of a combination of a fixed part and a movable part, and the pass range is selected by moving the movable part. 3 The fixed portion has two parts in each of the plurality of measurement meridian directions.
3. The eye refractive power measuring device according to claim 2, wherein the movable part has one pass zone in each of a plurality of measurement meridian directions. 4. The eye refractive power measuring device according to claim 1, wherein the diaphragm is capable of selecting the number of passing regions for the received light beam in all the measurement meridian directions among the plurality of measurement meridian directions. 5. The eye refractive power measuring device according to claim 1, wherein the diaphragm is capable of selecting the number of passbands for the received light beam in some of the measurement meridian directions among the plurality of measurement meridian directions. 6 a projection optical system that projects an index onto the fundus of the eye to be examined;
It has a light receiving optical system that receives the light flux reflected from the fundus, and an aperture that separates the projected light flux and the received light flux on a plane approximately conjugate with the pupil of the eye to be examined. In an apparatus for measuring eye refractive power, the diaphragm is capable of selecting the number of passbands for the received light flux in the measurement meridian direction, and when one passband is selected and the measured value reaches a predetermined value, the other passband is selected. An eye refractive power measuring device characterized in that it has a control means for selecting a range. 7. The control means first selects one passband for the received light flux in the measurement meridian direction and performs the measurement, and when the measured value is within a predetermined range, selects two passbands for the received light flux in the measurement meridian direction. The eye refractive power measuring device according to claim 6, which measures the eye refractive power by: 8. The control means first selects and measures two passing regions of the received light beam in the measurement meridian direction, and when the two index images of the optical position detection element interfere with each other, the control means selects and measures the received light beam in the measurement meridian direction. 7. The eye refractive power measuring device according to claim 6, wherein one passband is selected for measurement.