JPH0356046B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical system for reducing the minimum allowable pupil diameter for an eyeball function measuring device suitable for use in measuring the eyeball function of young and middle-aged and elderly people. It is.

[Prior art] In recent years, it has become possible to easily measure refraction and accommodation of the eye using autorefractometers and three-dimensional optometers, but the infrared rays used for measurement
Due to the power and size limitations of the LED, the minimum pupil diameter that can be measured is approximately 3 mm.

When healthy adolescents look at the far point (the farthest point they can see), almost all
Since the pupil diameter is above, the above-mentioned minimum pupil diameter is not a problem, but young people, middle-aged and elderly people generally have a pupil diameter of 3 mm or less even when looking at a far point. In addition, when the eyes adjust to look close, miosis occurs, and even in adolescents, miosis occurs by 3 mm.
It is often the following. Therefore, it is strongly desired to reduce the allowable minimum pupil diameter to about 1.5 mm, which is about half the current value.

This will be explained in more detail with reference to FIGS. 4 to 6.

FIG. 4 shows the optical system of an existing autorefractometer, and FIG. 5 shows the principle of its light projection system. In the optical system shown in these figures, images of two light sources LED as shown in Fig. 6 are projected onto the cornea of the test subject's eye e through lens L1, diaphragm (small hole) D, lens L2, and beam splitter BS. The measurement is performed by shining measurement light onto the retina through the LED window. Therefore, when the pupil becomes smaller, the amount of light to be measured decreases and a measurement error occurs, so the minimum pupil diameter is determined by the size of the image.

The light-receiving measuring device of this autorefractometer receives the reflected light from the fundus of the eye and performs the necessary measurements, and the reflected light is transmitted to the beam splitter.
The light is projected from the BS onto the photocell PC via an optical system including lenses L5 to L7, L9, a lens L8 controlled together with a diaphragm D, and the like. In addition,
The focal length of each lens in the figure is indicated in parentheses.

To give an overview of the measurement using the autorefractometer, first, images of the two light sources LED are formed on the cornea, and through the windows, an image of the diaphragm D is formed on the retina. Eye e is diaphragm D
When the image is accurately focused on the position of the image by the lens L2, the two light sources of the diaphragm D
The image produced by the LED is formed as a single point on the retina.

If diaphragm D located at point A, which is distanced from lens L2 by focal length f, moves from that position by x toward lens L2, and the eye is accurately focused on the image of diaphragm D formed by lens L2, the retina The image of is from the lens L7 at its focal length f
The lens can be placed at a position further away from point E by x in the direction of lens L7.

Therefore, when the lens L8 is moved toward the lens L7 by x in accordance with the movement of the diaphragm D, a conjugate image of the retina is formed on the photocell PC. Therefore,
By moving the diaphragm D and the lens L8 in conjunction so that the retinal image of the diaphragm D becomes one point on the photocell PC, the amount of adjustment can be measured from the amount of movement x.

As mentioned above, in the optical system of an autorefractometer, the minimum pupil diameter is determined by the size of the images of the two light sources LED formed on the cornea of the subject's eye e. two light sources
The distance between the centers of the LEDs is approximately 4 mm, and by setting f ₂ = 1/2f ₁ > f and creating an image on the cornea that is half the size of the light source LED, the minimum pupil diameter is approximately 3 mm.

This minimum pupil diameter can be easily halved by further doubling the focal length of f ₂ to make f ₂ = 4f, but in that case the amount of available light will be smaller than the distance. Since it is proportional to the square of the reciprocal, it is substantially less than 1/4, making measurement difficult.

[Problem to be Solved by the Invention] The technical problem of the present invention is to provide an optical system for reducing the minimum allowable pupil diameter in an eyeball function measuring device, which eliminates the decrease in light intensity due to the increase in focal length and makes the minimum pupil diameter sufficiently small. The purpose is to obtain a system.

[Means for Solving the Problems] To solve the above problems, the minimum allowable pupil diameter reduction optical system of the present invention is installed between the light projection system and the eye in an ocular function measuring device that measures refraction and accommodation of the eye. This optical system is characterized in that it is configured with an optical system that creates an enlarged image of the eye while preserving optical properties, and that the minimum allowable pupil diameter can be reduced.

[Function] Adding an optical system that creates an enlarged image of the eye while preserving its optical properties to the existing ocular function measurement device that measures refraction and accommodation of the eye eliminates the decrease in light intensity due to an increase in focal length and reduces the minimum pupil. It becomes possible to make the diameter sufficiently small.

[Example] An example of the minimum allowable pupil diameter reduction optical system according to the present invention will be described below with reference to FIGS. 1 to 3.

Figure 1 shows a known autorefractometer,
It shows the main parts of an optical system used in an ocular function measuring device that combines multiple optical elements to measure refraction and accommodation of the eye, such as a three-dimensional optometer, and more specifically, FIG. 4 shows an optical system corresponding to the light projecting system (FIG. 5) such as the autorefractometer described above. Therefore, in this optical system, optical elements corresponding to those in FIG. 5 are given the same reference numerals.

The minimum allowable pupil diameter reduction optical system of the present invention can reduce the minimum allowable pupil diameter by additionally installing it between the light projection system and the eye in an ocular function measuring device such as an autorefractometer. An optical system that creates an enlarged image of the eye while preserving its optical properties, that is, an optical system that preserves the property of converting parallel light into parallel light and maintains a constant magnification in the direction perpendicular to the axis. It is composed of

To explain this in detail with reference to Figure 1, when lens L3 (f ₃ = f) and lens L4 (f ₄ = f/2) are arranged as shown, the light emitted from point B will be directed to point D. The light that is condensed and parallel at point B becomes parallel light at point D, making it possible to construct an optical relay system that maintains almost its optical properties. In this optical relay system, the width of the parallel beam at point B is halved, and the magnification of the image at point B in the direction perpendicular to the optical axis is halved at point D. Conversely, if you place your eye on point D, the optical relay system will move your eye to point B.
An image twice the size of the eye is created at the point.

Now, in Fig. 1, if the eye is focused on the index T placed at a position moved by x from the small point position A of the lens L2, then based on Gauss's formula, the image distance is determined by the lens L2. b ₂ is b ₂ = (f-x)・f/(f-x)-f=-f ² /
Since it becomes x+f, from point B, the index T is placed at the position of f ² /x.
It looks like there is. Next, when the lens L3 acts on that image, the image distance b ₃ is b ₃ = (f + f ² /x) · f / (f + f ² / x) - f
=x+f.

Furthermore, due to the lens L4, the image distance b ₄ is: b ₄ = (f/2-X)・f/2/(f/2-X)
Since -f/2=-(f/2) ² /X+f/2, it appears that the index T is at a distance of (f/2) ² /x from point D.

When measuring with an autorefractometer, it is customary to define the reciprocal of distance (m) as diopter (D), so the measurement value obtained by adding such an optical relay system is multiplied by 4. By simply doing this, you can easily measure refraction and accommodation values by halving the minimum pupil diameter. In the above embodiments, the explanation has been made assuming that the minimum pupil diameter is set to 1/2, but it goes without saying that when the minimum pupil diameter is set to 1/n, the obtained diopter n may be multiplied ^{by 2} .

In addition, the present inventors have proposed an eyeball refractive power measuring device that can measure accommodation even when the eyes are moved freely, in Japanese Patent Application Laid-open No. 8730/1983 (Patent Application No. 146227/1982). .

This device consists of a light source unit equipped with a light source for irradiating the eyeball with a beam of infrared light, a direction measurement unit that detects changes in the orientation of the eyeball, and a real image of the eyeball on the reflective surface of a biaxially swinging mirror. a pair of opposing concave mirrors that form an image on the eyeball, an optical system that forms the real image as a second real image at a position opposite to a light source that is optically equivalent to the position of the eyeball, and a mirror rocking drive mechanism for making the second real image stationary by tilting it based on the output of the direction measuring section, regardless of changes in the direction of the desired ball; It is equipped with a refractive power measuring section that measures the refractive power of the eyeball based on positional deviation.The optical relay system in this device is designed to relay the image of the eye at the same magnification as shown in Figure 2. I think the relay system is basic.

However, by applying the principles of the present invention and using a lens system as shown in Figure 3, it is possible to double the image of the eye without impairing the optical properties, as described above. , it is possible to construct a three-dimensional optometer with a minimum pupil diameter of 1/2. In this case as well, setting the magnification to n is easy as in the above case.

[Effects of the Invention] As is clear from the detailed explanation above, according to the present invention, an enlarged image of the eye can be added to the existing ocular function measurement device for measuring refraction and accommodation of the eye while preserving the optical properties. By simply adding an optical system that creates a It can also be effectively used to measure the eyeball function of the following young and middle-aged and elderly people.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing the essential parts of the optical system of the present invention used additionally in a known eyeball function measuring device, and FIG. 2 is an optical relay system in the eyeball refractive power measuring device previously proposed by the present inventor. Figure 3 is an explanatory diagram of an optical relay system to which the principles of the present invention are applied, Figure 4 is a configuration diagram of the optical system of an existing autorefractometer, and Figure 5 is its light projection system. The principle configuration diagram, Figure 6, shows the structure on the cornea.
FIG. 3 is an explanatory diagram of an image of an LED.

Claims (1)

[Claims] 1. An optical system that is additionally installed between the light projection system and the eye in an ocular function measuring device that measures refraction and accommodation of the eye, and that creates an enlarged image of the eye while preserving its optical properties. An optical system for reducing the minimum allowable pupil diameter for an ocular function measuring device, characterized in that the minimum allowable pupil diameter can be reduced.