JPS6341579B2 - - Google Patents

Description

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

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.

However, in this type of device, when separating the fundus reflected light flux and making it incident on the optical position detecting element, two images A and B are sent to the optical position detecting element C as shown in Fig. 1.
Since the image is projected upward and the image interval D is measured, when the image changes due to refractive error of the subject's eye, for example, image A
is displaced to the position A', and the image B is displaced to the position B', spreading to the image interval D' on the optical position detection element C.
Here, the image interval D' can detect changes from 0 to the maximum and the length l of the optical position detection element C, and the image A
The detectable displacement amount of and B is 1/2, but in reality, both ends and the center of the optical position detection element C cannot be detected from the viewpoint of signal processing, so it is shorter than 1/2. 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 C, 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 addition, if a long optical position detection element is used to expand the measurement range or improve resolution, the fundus of the optical system must be Since it is necessary to take a long optical path from the surface that separates the reflected light beam to the surface of the optical position detection element, there is a drawback that the entire device must be large-sized.

An object of the present invention is to improve the above-mentioned problems by making it possible to detect the position of the reflected light beam from the fundus over a wide range using an optical position detection element of a certain length, thereby expanding the measurement range and improving the resolution of position detection. The purpose is to provide an eye refractive power measurement device that can be set in detail and can measure refractive power with high precision and high speed. An apparatus comprising a light receiving optical system that separates the reflected light beam into a plurality of light beams on a plane substantially conjugate with the pupil of the eye to be examined, and detects the imaging position of these separated light beams using an optical position detection element,
a storage means for causing a preset reference light beam to enter the optical position detection element to output an electrical signal corresponding to the position of the light beam and storing the output as a reference value; and a storage means for storing the output as a reference value; It is characterized by comprising a storage means for storing the output of the corresponding optical position detection element, and a calculation means for reading out the stored reference value and the stored output of the optical position detection element and performing a comparison operation. be.

The present invention will be explained in detail below based on the embodiments shown in FIG. 2 and below.

FIG. 2 shows an embodiment of the present invention,
a projection optical system on an optical axis 01 coaxial with the axis of the eye E to be examined;
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, a projection mask 3, a relay lens 4, an aperture plate 5, a perforated mirror 6, and an objective lens 7, which are arranged sequentially from the side farthest from the eye E to be examined. It is configured. As shown in FIG. 3, the projection mask 3 has linear slits 3a, 3b, and 3c that are set at an angle of 120 degrees to each other and perpendicular to three predetermined meridians, respectively. The slits 3a to 3c serve as charts for measurement. Also,
The aperture plate 5 has a circular aperture on the optical axis 01.

The light receiving optical system arranged on the reflection side of the perforated mirror 6 includes a three-hole diaphragm plate 8, a relay lens 9, a prism 10, and cylindrical lenses 11a, 11b, 1
1c, and optical position detection elements 12a, 12b, and 12c. As shown in FIG. 4, the three-hole aperture plate 8 has three fan-shaped openings 8a, 8b, and 8c arranged in the meridian direction. Furthermore, as shown in FIG.
0b and 10c, these prisms 10a
10c are arranged to cover the openings 8a to 8c, respectively. Therefore, the light beams passing through the apertures 8a to 8c are refracted in each meridian direction and separated from each other.

In order to receive this separated light flux, the cylindrical lenses 11a to 11c and the optical position detection elements 12a to 12c are arranged in pairs and aligned with each meridian centering on the optical axis 02, as shown in FIG. has been done. That is, each cylindrical lens 11
A to 11c are arranged such that their generatrix lines coincide with the meridian, and when a one-dimensional photodiode array is used, the optical position detection elements 12a to 12c are arranged so that the direction in which the photodiodes are lined up coincides with the meridian.

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. In addition, the projection mask 3 is a relay lens 4.
is conjugate with the focal plane F, and each light receiving surface of the optical position detection elements 12a to 12c is connected to the relay lens 9.
is conjugate with the focal plane F with respect to Furthermore, the diaphragm aperture plate 5 is configured to adjust the pupil Ep to the subject's 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 Ep. The three-hole diaphragm plate 8 is also conjugate with the pupil Ep with respect to the objective lens 7, and among the light beams reflected by the fundus Er, the light beams from three places around the pupil Ep pass through each aperture 8a to 8c of the three-hole diaphragm plate 8. pass. The cylindrical lenses 11a to 11c can condense and guide the light from the slit portions to the respective optical position detection elements 12a to 12c 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 8a to 8c of the three-hole diaphragm plate 8. Then, it is subjected to an imaging action by the relay lens 9, deflected in each imaging direction by the prism 10, and the cylindrical lens 1
The light is condensed by the unidirectional refractive power of 1a to 11c, and is imaged at one point on each of the optical position detection elements 12a to 12c.

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 12a to 12.
A clear image is formed on c. In this state, the polarization angle of the prism 10 and each optical position detecting element 12a to 12c are set so that the image forming point on each optical position detecting element 12a to 12c reaches the optical position detecting element near the center of the photometric length.
Select the location.

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 of the apertures 8a to 8c of the three-hole diaphragm plate 8 and entering the prism 10 via the relay lens 9 changes depending on the diopter. Therefore, the image position on each optical position detection element 12a to 12c 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.

FIG. 7 shows the relationship between the chart image on the optical position detecting element 12a, and when the eye E to be examined is emmetropic, the chart image on the optical position detecting element 12a is at the position P1,
This indicates that when the eye is myopic, the image is formed at the position P2, and conversely, when the eye is farsighted, the image is formed at the position P3. In addition,
Although the chart images on the optical position detection elements 12a to 12c will be somewhat blurred, position detection can be performed without any problem by increasing the F number of the optical system and increasing the depth of focus.

Next, signal processing of the output signals of the optical position detection elements 12a to 12c will be explained with reference to FIG. In FIG. 8, the above-mentioned optical position detection elements 12a to 12a, each consisting of a one-dimensional photodiode array, for example.
12c stores the brightness and darkness of the projected chart image. The channel selection signal S1 outputted from the microcomputer 13 via the interface circuit 14 causes the analog multiplexer 1 to
5 is switched to the a channel, and the read signal Sa is applied to the optical position detection element 12a via the drive circuit 16a. As a result, the analog signal S2 corresponding to brightness stored in the optical position detection element 12a is extracted, and after being amplified by the amplifier 17a, it is passed through the analog multiplexer 15 to the sample hold circuit 18 and the analog/digital converter 1.
9, it is converted into a digital signal S3. and,
The data is stored in a read/write memory (RAM) 21 via an interface circuit 14 and a microcomputer 13. Similarly, optical position detection elements 12b, 1
2c 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 21.

In FIG. 8, 22 is a programmable read-on memory (PROM), and based on this information, the microcomputer 13 calculates which position on the optical position detection elements 12a to 12c is the brightest.

At the manufacturing stage of this device, the device is operated for adjustment, and a flat reflector having a property of scattering and reflecting is installed on the focal plane F. It is desirable that the scattering characteristics and reflectance be as close as possible to those of the fundus of the human eye. The chart image is reflected by this plane reflection plate, and as shown in FIG.
2a, and the optical position detection element 12
Images are similarly formed on b and 12c. The outputs of the optical position detection elements 12a to 12c at this time are read out and stored in the programmable read-only memory 22 as position information. That is, the programmable read-only memory 22 stores reference positions corresponding to the normal eye of the optical position detection elements 12a to 12c of each of the channels a to c.

In this adjustment process, instead of installing a plane reflector on the focal plane F, a tool such as the one illustrated in FIG. 9 may be used. That is, in FIG. 9, 23 is a lens barrel that holds the above-mentioned objective lens 7, and is a part of this apparatus. This tool includes an imaging lens 24,
It is composed of a flat reflecting plate 25 and a cylinder 26 that holds them. Here, the imaging lens 24 has such power that a slit image is formed on the plane reflecting plate 25. If this tool is connected to the lens barrel 23 of the objective lens 7, the same effect as when a flat reflector is installed on the focal plane F can be obtained, and each channel a
The reference positions of ~c can be stored in the programmable read-only memory 22. Note that this tool can also be used as a check tool for maintenance and inspection of this device, and using this tool makes maintenance and inspection extremely easy.

This completes the process at the manufacturing stage of this device, and the plane reflector or the aforementioned tool is removed. When actually measuring the eye refractive power, if the eye E to be examined has a refractive error, the position of the chart image will shift from the reference position of each optical position detection element 12a to 12c according to the degree of abnormality. The image forming position is detected by the action of the signal processing circuit system shown in the figure and stored in the read/write memory 21.

The microcomputer 13 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 22 stores in advance a mathematical formula for converting this amount of deviation into a diopter, and based on this information, the microcomputer 13 calculates the diopter for each meridian. In this way, by measuring the diopter in the three meridian directions, the degree of astigmatism (SPH), astigmatic axis angle (CLY), and spherical diopter (AX) are calculated.
The numerical value is displayed on the numerical display 20.

FIG. 10 is a flowchart illustrating the above procedure, and the writing of the reference positions of the optical position detection elements 12a to 12c, which is performed at the manufacturing stage of the device, is omitted.

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. Furthermore, manufacturing errors when incorporating the optical position detection element do not affect measurement accuracy, and accurate measurement values can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between a projection chart and an optical position detection element in a conventional eye refractive power measuring device, and Fig. 2 and the following show examples of the eye refractive power measuring device according to the present invention. Layout diagrams, Figures 3 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, and Figure 9 is a diagram of the relationship between the chart image and the optical position detection element. FIG. 10 is a sectional view of a tool for determining a reference position on the optical position detection element, and is a flowchart of the measurement procedure. Reference numeral 1 is a light source, 2 is a condenser lens, 3 is a projection mask, 4 is a relay lens, 5 is an aperture plate, 6 is a perforated mirror, 7 is an objective lens, 8 is a 3-hole aperture plate, and 9 is a relay lens. , 10 is a prism, 11a
~11c is a cylindrical lens, 12a~12
13 is a microcomputer, and 22 is a programmable read-only memory.

Claims (1)

[Scope of Claims] 1. A projection optical system that projects a chart onto the fundus of the eye to be examined, and separates the light beam reflected from the fundus into a plurality of light beams at a plane substantially conjugate with the pupil of the eye to be examined, and forms a resultant of these separated light beams. A device having a light receiving optical system for detecting an image position by an optical position detecting element, the apparatus comprising: a light receiving optical system that detects an image position by an optical position detecting element, which makes a preset reference light beam enter the optical position detecting element and outputs an electric signal corresponding to the position of the light beam; storage means for storing the output as a reference value; storage means for storing the output of the optical position detection element corresponding to the imaging position of the separated light beam; and the optical position detection element in which the reference value and the stored reference value are stored. 1. An eye refractive power measurement device comprising: arithmetic means for reading out outputs of and performing comparison calculations. 2. The eye refractive power measuring device according to claim 1, wherein the fundus reflected light is separated into three radial directions. 3. The eye refractive power measuring device according to claim 1, wherein the reference value is determined by installing a reflector in the optical system at a position conjugate with the fundus of the eye during the adjustment stage. 4. The eye refractive power measuring device according to claim 3, wherein the reflecting plate is combined with an imaging lens and combined with an objective lens of the device.