JPS5848170B2 - Menu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for determining the refractive power of an eye by detecting the far point or near point of the eye, in which an optotype that a subject looks at and the subject's retina are optically connected. The present invention provides a novel configuration characterized in that the far point or the near point is determined by objectively detecting the limit of possible conjugation using the fact that the object becomes conjugate.

Conventionally, Bausch &Lomb's Safil is a device that independently detects the refractive state of the eye. Although the ophthalmetron is known, the device is complicated, and in particular, it follows a principle that strictly matches the main optical axis of the device and the optical axis of the subject's eye, so it is difficult to align the optical axis. A means of securing the subject and a system for immobilizing the subject were required.

Furthermore, even if the subject is fixed, there is no guarantee that the eyes will not move, so there is a risk that the optical axis will shift and detection errors will occur.

Furthermore, from the point of view of use, since the above-mentioned optical axis alignment procedure is required, handling cannot be said to be easy.

The present invention solves the above-mentioned conventional drawbacks, and has a simple configuration, no fear of error, and an eye refractive power detection device that can objectively detect the far point or near point of the eye by handling without requiring skill. The purpose is to provide new services.

The present invention will be explained below according to the illustrated embodiments.

FIG. 1 shows a first embodiment of the present invention, in which 1 is an eyepiece;
Reference numeral 2 denotes a block whose distance from the eyepiece is variable by a motor (not shown) or the like, and its movement is recorded on a stationary recording paper (not shown) by a recording pen 2a fixed to the block.

The following are members fixedly installed in the block, 3 is an optotype, and 4 is an optotype illumination lamp.

5 is a half mirror, and 6 is a light shielding plate provided on the half mirror 5 at a position optically equivalent to the optotype 3, and has a slit 6a.

Reference numeral 7 denotes a light source lamp, which allows light in the specific wavelength range to enter the subject's eye 9 through the slit 6a via a filter 8 that transmits only light in the specific wavelength range.

10 is a prism having a semi-transparent surface 10a therein, and 11 is a light shielding plate having a slit Nla of the same shape at a position optically equivalent to the above-mentioned slit 6a on the semi-transparent surface 10a.

A light receiving element 13 is provided behind the slit 11a via a filter 12 which has the same properties as the filter 8 and is used to remove noise due to light outside the specific wavelength range.

With the above configuration, the block 2 is configured such that the optotype 3 is the eyepiece 1
This is a means for determining whether or not the crystalline lens 9a of the subject's eye is in a position optically conjugate with the retina 9b of the subject's eye, and the principle thereof will be explained here.

Now, if we consider the case where the subject's eyes can clearly see the optotype 3, the image of the optotype 3 is formed on the retina 9b.

Generally, in such a case, assuming that light comes out from the retina, the image will be formed at the position of the optotype 3.

That is, the landmark 3 and the retina 9b are in an optically conjugate relationship.

Now, as mentioned above, the optotype 3 and the slit 6a are provided at optically equivalent positions, so the retina 9b is the slit 6a.
It is also optically conjugate with a.

Therefore, the image of the slit 6a produced by the light source 7 is also formed on the retina.

Furthermore, the slit image on the retina is diffusely reflected by the retina, which means that a new light source in the shape of the image of the slit 6a has been generated on the retina.

Here, since the slit }1 1a is located at the optically equivalent position to the slit }6a on the semi-transparent surface 10a as described above,
The retina 9b is also optically conjugate with the slit 11a.

Therefore, the light reflected from the image portion of the slit 6a on the retina passes through the crystalline lens 9a and the eyepiece 1, transmits the half mirror 5, is further reflected by the semi-transparent surface 10a, and forms an image again at the position of the slit N1a. do.

Since the light receiving element 13 receives the light that has passed through the slit 11a via the filter 12, it receives all the light that has reached the light shielding plate 11, and at this time, the amount of light received is maximum.

On the other hand, considering the case where the subject's eyes cannot clearly see the optotype 3, the slit 6a and the retina 9b are not optically conjugate, as is clear from the above.

Therefore, the image of the slit 6a becomes a blurred and spread image on the retina 9b.

Furthermore, since the slit N Ia and the retina 9b are not optically conjugate, the light that uses the blurred slit image on the retina as a new light source further spreads when it reaches the position of the slit 11a, resulting in a blurred image. .

Therefore, the part that spreads due to blur is cut by the light shielding plate 11, and the light receiving element receives only 5 of the light that reaches the light shielding plate 11.
This is only a small part of the area of the slit Nla, and the amount of light received becomes small.

Next, a case in which measurement is performed using the above embodiment will be described.

For example, when the movement of the block 2 is controlled by the landmark 3, the eyepiece 1
It is assumed that the measurement is performed starting from a position that is internally located from the focal point of the lens, and moving in a direction in which the optotype moves away from the lens.

At the starting point of the movement, the optotype 3 is located at a distance from the focal point of the lens 1, so the light emitted from one point on the optotype is diverged between the lens 1 and the crystalline lens 9a in the direction toward the crystalline lens.

This applies when the eyes 9 are looking at an object at a short distance.

Therefore, the eye adjusts the crystalline lens 9a and focuses on the optotype 3, so that the retina and the optotype are optically conjugated, and the output of the light receiving element is at its maximum value.

As the block 2 is moved from this state, the optotype 3 gradually approaches the focal point of the lens 1.

In other words, the visual target 3 gradually comes to correspond to an object located at a far distance.

In this process, the accommodation power of the crystalline lens 9a reaches its limit and it becomes impossible to focus on the optotype 3 any more, but at this time the optotype and the retina are no longer optically conjugate, so the output of the light receiving element is Decrease rapidly.

Therefore, if the position of the block 2 at the critical point where the amount of received light begins to rapidly decrease is recorded with the recording pen 2a, this will indicate the far point of the eye.

This relationship is shown in the graph of FIG.

In this graph, the amount of light received gradually decreases because
This is because the retina and the light receiving element gradually move away from each other.

A normal eye can focus on the optotype 3 until infinity, that is, until the speed of light entering the crystalline lens becomes parallel.

In other words, the critical point coincides when the visual target 3 comes to the focal point of the eyepiece 1.

On the other hand, in the case of myopic eyes (FIG. 2 shows this case as an example), the critical point is reached when the optotype 3 is still within the focal point of the lens 1.

In addition, in the case of hyperopic eyes, even if the light beam incident on the crystalline lens is convergent light, it can be focused on the optotype 3.
The critical point is reached when the focal point of the lens 1 is located outside the focal point of the lens 1.

The above is an explanation for finding the far point, but when finding the near point, the retina 9b and the optotype 3 will no longer be optically conjugate if the optotype becomes closer than the accommodating power of the crystalline lens, so do the same thing. can be measured.

In the above, it is desirable to use filters 8 and 12 that transmit only infrared light.

This is because the reflectance of the retina of the eye is large in the infrared region.

Further, the member 14 in the above embodiment is thus a correction plate for correcting the optical path length when the optotype illumination light and the light emitted from the slit 6a are in different wavelength ranges.

Reference numeral 14a denotes a color filter, which is not necessary when viewing the optotype with white light, but is used when it is desired to measure the refractive power of a specific color.

At this time, the correction plate is selected to be suitable for correcting the optical path length of the light of the specific color and the infrared light, and is usually replaced in pair with the color filter.

Note that for optical path length correction, instead of using the correction plate 14, the optotype 3 itself may be moved relative to the slit 6a.

Furthermore, in the above, the half mirror 5 may be replaced with a dichroic filter selected to have a characteristic of transmitting only the infrared region and reflecting light in other wavelength regions, and configured to prevent a reduction in the amount of target light. good.

FIG. 3 shows a second embodiment of the invention, in which common parts are given the same numbers as in FIG.

In this embodiment, a block 2 indicated by a broken line does not move in the optical axis direction, and has an eyepiece lens 1 constituted by a varifocal lens system with a variable focal length inside.

That is, here, the change in the relative position between the optotype and the focal point of the eyepiece is not done by moving the block in the optical axis direction, but by changing the focal length of the eyepiece 1, and the state of the change is determined by the change in the focal length of the eyepiece. Recording is performed by a recording pen 1a that is linked to a focal length changing mechanism.

Further, the optotype 3 here consists of a filter that blocks only light in the infrared region, and has a slit 3a in a part thereof.

That is, since the raft mark 3 also serves as the slits 6a and 11a in the first embodiment, there is no need for adjustment to arrange these three parts optically equivalently, making assembly easy.

The light source lamp 7 also serves as an optotype illumination lamp, and makes the optotype visible with the light that does not contain infrared light that has passed through the optotype 3, and also makes the optotype visible through the light that contains infrared light only at the slit 3a. Inject it into the .

Further, between the light source lamp 7 and the optotype, a focusing lens 15,
An ND filter 16 and a half mirror 17 are arranged.

The ND filter 16 moderately absorbs light outside the infrared region,
To obtain sufficient infrared light, the spectrum of the light source is adjusted so that the visual target will not be dazzled by visible light even if the light source is strengthened.

The half mirror 17 reflects light including infrared light that has been reflected from the retina 9b of the eye and passed through the slit 3a of the optotype 3 toward the light receiving element 13.

The filter 12 that transmits only the infrared range cuts light in other wavelength ranges, so that of the light that enters the slit 3a, only the infrared light that is emitted from the slit 3a and reflected by the retina 9b is filtered. The light should reach the light receiving element 13.

In addition, the optical path length correction plate 14 and the color filter 14a are provided with a slit N4b so as not to obstruct the infrared light passing through the slit 3a.
has.

With the above configuration, in this embodiment, as in the first embodiment, the retina 9
When b and the visual target 3 are optically conjugate, the amount of light received is maximum.

When using this example, the focal length of the lens 1 is lengthened so that the optotype 3 is positioned inward of the focal point of the lens 1 at the starting point of measurement, and the focal length is changed so that the focal length is gradually shortened. By operating the mechanism, results similar to those of the first embodiment can be obtained.

Furthermore, the above embodiment further includes a mechanism 18 that rotates the entire block 2 around the optical axis, and by measuring the degree of refraction in each direction around the optical axis, it is possible to measure astigmatism. ing.

FIG. 4 shows the angular relationship between the slit 3a and the eye 9 around the optical axis, and in the illustrated state, the refractive power in the O0 direction is measured.

That is, when considering how the degree of blurring affects the amount of light received when the reflected light from the retina 9b reaches the slit 3a, we can see that for the blur in the direction of the arrow A perpendicular to the slit 3a, It can be seen that although the amount of received light changes sharply, the blurring in the direction along the slit has a slow influence on the change in the amount of received light.

Therefore, the refractive power in the direction of arrow A is selectively measured.

If block 2 is rotated based on the above principle, slit 3
Since a also rotates, the refractive power in each direction perpendicular to the slit can be measured.

By plotting the measurement results in each direction, the state of astigmatism of the eye can be detected.

FIG. 5 shows that using the second embodiment shown in FIG. 3, the angles are determined as shown in FIG. 4, and the focal length corresponding to the far point is measured at each angle. This is a graph showing the relationship between angle and refractive power, converted to one unit of refractive power.

As is clear from the figure, since the refractive power changes depending on the angle, it can be seen that the eye to be examined is astigmatic.

FIG. 6 shows a third embodiment of the present invention, and parts common to the above embodiments are designated by the same reference numerals.

The optical part of this embodiment differs from the above embodiments in the members 19 and 20, and the others are essentially the same, so only this member will be described.

19 is a mirror having a slit-shaped transparent portion 19a at a position optically equivalent to the optotype 3 for the half mirror 5; 20 is a filter surface 20 having the same properties as the filter 8;
It is a prism with a.

In this embodiment, the light emitted from the light emitting diode 21 (light source rung) passes through only the transparent portion 19a of the mirror and enters the eye.

If the transparent portion 19a and the retina 9b are conjugate, the reflected light from the retina is re-imaged on the transparent portion and passes through it, so that it is not reflected by the mirror 19 and passes through the light receiving element 13.
does not reach.

On the other hand, if the light is conjugated, the reflected light will be blurred and spread out when it reaches the transparent part.

Therefore, as shown by the dashed line in the figure, the light that deviates from the transparent portion is reflected by the mirror 19 and guided into the prism 20, reflected on the inner surface of the prism, passes through the filter 20a, and then reaches the light receiving element 13.

As described above, in this embodiment, when the slit-shaped transparent portion and the retina are optically conjugate, the amount of light received by the light receiving element is minimized.

Note that 22 is a focal length changing mechanism of the eyepiece lens 1, which moves a part of the varifocal lens system constituting the eyepiece lens in the optical axis direction in order to change the focal length.

23 and below show each block of a circuit for temporarily storing measurement results and speeding up measurement.

In this embodiment, the rotation mechanism 18 rotates the block 2 at high speed, whereas the focal length changing mechanism 22 changes the focal length of the eyepiece relatively slowly.

A shaft encoder 23 is connected to the rotating mechanism 18 so as to divide the rotation of the block 201 into equal parts and output one pulse each time the equal dividing point passes.

The pulses are counted by the first counter 24, and the count output is sent to the first memory circuit 25 as a rotational position address signal.
and is input to the second memory circuit 30.

On the other hand, an oscillator 26 is connected to the light emitting diode 21, and the diode is caused to emit light intermittently.

A tuning amplifier 27 intermittently sends the output of the light receiving element to the analog-to-digital converter 28 in synchronization with the oscillation of the oscillator 26.

This process serves as a means of removing noise.

The converter 28 digitizes the instantaneous output from the tuned amplifier 21 in response to the pulses from the shaft encoder 23.

Let this digital amount be data A. The pulses from the shaft encoder 23 simultaneously read out the digital amount stored in the memory circuit 25 corresponding to the same rotational position address signal from one revolution before.

Let the read digital amount be theta B. The digital comparator 29 compares the two data A and B, and if the new data A is smaller than the read data B, sends a write command to the first memory circuit 25 and the second memory circuit 30.

The first memory circuit 25 reads data A and data B.
Replace.

A linear encoder 31 is associated with the mechanism 22 so as to output pulses one by one as the movable part of the varifocal lens system moves in the optical axis direction.

32 is a second counter, and the count value is inputted to the second memory circuit 30 as data.

The second memory circuit 30 reads the count value in response to a write command from the comparator 29 and rewrites the previous count value data.

If the relationship between data A and B is B<A, no write command is sent, and data is not replaced in both the first and second memory circuits.

After performing this process for all steps of focal length change, the data remaining in the second memory circuit 30 is stored in block 2.
This is a count value indicating the focus position that provides the minimum output at each rotational position address.

As is clear from the above, the capacity of the first and second memory circuits needs to accommodate data equal to the above-mentioned equal number of rotations of 201 blocks.

Naturally, the first memory circuit 25 must initially contain the maximum value (that is, in the case of a binary number, each digit is 1).

Note that the slit 6a of the light shielding plate in all the above embodiments
, 11a or the slit 3a of the filter, or the transparent part 19a of the mirror, instead of using it as a slit, the pinhole 33 as an example as shown in FIG. 7 or the half thereof as shown in FIG. Similar effects can be obtained by replacing the light shielding plate (or filter, or mirror) 34 with the portion 34a.

Since the present invention follows the principle and configuration as described above, the basic structure is simple.

More importantly, since misalignment of the optical axis does not cause errors, there is no need for strict means of optical axis alignment, and since there is no procedure for optical axis alignment, it is easy to use and does not require any skill to operate. That's what happened.

This is due to the fact that it is detected that the optotype and the retina are optically conjugate, and even if the optical axis is misaligned, if they are conjugate, the light emitted from the exit slit This is due to the fact that the image is always refocused at the position of the light receiving slit.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of the first embodiment of the present invention, and Fig. 2 is a cross-sectional view of the first embodiment of the present invention.
FIG. 3 is a graph showing an example of the measurement results according to the example.
4 is an explanatory diagram of the angular relationship between the slit and the eye in the second embodiment, FIG. 5 is a graph showing an example of the measurement results according to the second embodiment, and FIG. The measured sectional view of the third embodiment, FIGS. 7 and 8 are front views showing modifications of the main parts of the optical system of the present invention. 1...Eyepiece, 3...Optotype, 3a
, 6a, 11a, 19a...Slit, 1...
...Light source lamp, 9...Eye, 9b...
...Retina, 13... Light receiving element.

Claims (1)

[Claims] 1. In an eye refractive power detection device having an eyepiece, an optotype, and an optical distance variable means for changing the optical distance between the optotype and the subject's eye, the position of the optotype or A light-emitting means that emits light from a single light-emitting section at a position conjugate to this toward the subject's eye, and the light-emitting section that emits light emitted by the light-emitting means and reflected on the retina of the subject's eye. Alternatively, an eye refractive power detection device comprising a detection means for detecting the magnitude of the amount of light in an optically conjugate portion.