JP3207510B2 - Eye measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring-shaped illumination light irradiating section for irradiating a ring-shaped illumination light to a cornea of an eye to be examined, and receives a ring-shaped opposite image formed by corneal reflection of the illumination light. The present invention relates to an eye measurement apparatus that includes an image receiving optical system and determines a relative positional relationship between a main device and an eye to be inspected based on the ring image.

[0002]

2. Description of the Related Art Conventionally, a measuring apparatus for an eye to be inspected, for example, a cornea of an eye to be inspected is irradiated with ring-shaped illumination light, and the reflected light of the illumination light on the cornea surface is observed as a ring image. In a keratometer that measures the radius of curvature of the cornea using or determines the relative position between the main device and the cornea,
In many cases, the ring image to be observed is projected on a monitor or the like, and alignment is performed to photograph the ring image.

In this case, the state of the ring image to be photographed is often visually judged by the examiner, and whether or not the state of the ring image can be accurately measured is left to the judgment of each examiner. That is the fact.

[0004]

By the way, in such a conventional eye measuring apparatus, when alignment is completed and the eye to be inspected is measured, an image is taken by the movement of the eye to be inspected, the movement of the eyelid, and the like. In some cases, the obtained image is not suitable for measurement. That is, when the eye to be examined moves, the ring image moves due to the movement, and the ring image may be lost. Also,
An eyelid image may be captured at the same time, and there is a problem that an error occurs in the detection of the ring image and an error occurs in the measurement result.

[0005] Moreover, after capturing these images,
Although it is possible to check these, it takes time to check the image, and after that, it is necessary to take a picture again, which wastes time.

Therefore, the present invention provides an eye measuring apparatus for an eye which can check whether or not a ring image is in a predetermined state and whether or not an image of an eyelid is reflected, at a speed close to real time. The purpose is to provide.

[0007]

In order to solve the above-mentioned problems, a measuring device for an eye to be examined according to the present invention comprises: a ring-shaped illumination light irradiating section for irradiating a ring-shaped illumination light to a cornea of an eye to be inspected;
A light receiving optical system that forms a ring-shaped opposite image formed by corneal reflection of the illumination light as a plurality of ring images of different magnifications, and a light receiving optical system that forms the ring images. Radially arranged on a conjugate plane substantially conjugate with the image forming plane with an optical axis orthogonal to the conjugate plane as a center, and obtained at different magnifications.
A plurality of one-dimensional light receiving elements that receive the plurality of ring images, and the one-dimensional light receiving element based on an output signal from each one-dimensional light receiving element.
The gist is that a signal processing circuit for determining whether or not a plurality of ring images are in an appropriate state is provided.

[0008]

According the eye measurement apparatus according to the present invention, the irradiated ring-shaped illumination light to the cornea of the eye from the ring-shaped illumination light emitter, the ring by the illumination light corneal reflection
As ring images of different magnifications as opposite images
The light receiving optical system is formed.

At this time, a plurality of one-dimensional light receiving elements are disposed at positions substantially conjugate with the image planes of a plurality of ring images of different magnifications and radially around an axis coaxial with the optical axis of the light receiving optical system. At the same time, a plurality of ring images having different magnifications are formed, and output signals from these one-dimensional light receiving elements are input to a signal processing circuit to determine whether the plurality of ring images having different magnifications are appropriate.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an eye length measuring apparatus according to an embodiment of the present invention;

(First Embodiment) FIG. 1 shows an embodiment of the present invention, and FIG. 1 (A) is a side view of an external appearance of an eye axial length measuring device.
(B) is a block diagram similarly.

In FIG. 1A, an axial length measuring device 1 is shown.
A measuring unit 3 movably provided on the gantry 2; a subject fixing unit 4 for receiving a jaw and a forehead of a subject (not shown); An alignment mechanism 5 for moving the measuring unit 3 is provided.

The alignment mechanism 5 fixes the face of the subject to the subject fixing part 4 when measuring the subject's eye.
For example, the configuration is such that the alignment unit 5 is operated using the joystick 6 to move the measuring unit 3 to a correct position with respect to the eye E of the subject.

Therefore, when the axial length is measured by the axial length measuring apparatus 1, first, the measuring unit 3 is properly aligned with the eye E, and the cornea described later is observed while observing the anterior segment of the eye E. A ring reflected light is searched for, and the measurement unit 3 is aligned with the best focus position for measurement. However, when the measurement of one subject is completed and the next subject is to be measured, the same operation must be performed again.

At this time, if the measuring unit 3 is kept at the position where it was placed at the end of the measurement of the first subject, the best focus position will be obtained when the next subject puts his face on the subject fixing unit 4. Therefore, the examiner needs to determine the image of the anterior eye part shown on the monitor 3a and the focus state of the corneal reflected light and move the measuring unit 3 back and forth.

This judgment must be made with intuition. That is, the positional relationship between the cornea and the chin / forehead varies depending on the skeleton of the subject, and in the case of this measurement, the best focus position of the corneal reflection slightly varies depending on the radius of the corneal curvature of the eye E. The position must be determined each time. In addition, when the measurement unit 3 is close to the subject fixing unit 4, when the subject puts his / her face, there is a feeling of oppression and an unnecessary psychological burden is given to the subject.

Therefore, the face of the subject, that is, the subject's eye E,
If the measuring unit 3 is returned to the reference position once when it comes off the subject fixing unit 4, it is easy to handle and the psychological burden on the subject can be reduced.

For this reason, as shown in FIG. 1 (b), the apparatus for measuring the axial length of the eye used here is a means for determining whether or not the face of the subject is in contact with the subject. 7
And a reference position return mechanism 8 for moving (retreating) the measuring unit 3 to a reference position (a position indicated by a chain line in FIG. 1A) in accordance with an output from the eye presence / absence determining means 7.

The eye-to-be-examined judging means 7 is provided on either the chin rest 4a or the forehead rest 4b of the subject-fixing part 4, and is disconnected when the face is in contact with the subject-fixing part 4. A switch 7a and a signal circuit 7b for outputting a high-level / low-level signal according to ON / OFF of the switch 7a
And

The reference position return mechanism 8 includes a mechanism member 8a such as a motor or a clutch for moving the measuring section 3 to the reference position in accordance with the high / low signal output from the signal circuit 7b, a motor / clutch drive circuit 8b, Reference position sensing means 8c for outputting a signal when the measurement section 3 is at the reference position.

When the subject has his / her face in contact with the subject fixing section 4, the switch 7a is turned off, and the signal circuit 7b outputs a low-level signal. On this occasion,
The motor / clutch drive circuit 8b controls the mechanism member 8a to disconnect the clutch and disconnect the connection to the motor and stop driving the motor. In this state, the measuring section 3 can be freely moved back and forth and right and left.

On the other hand, when the subject removes his / her face from the subject fixing unit 4, the switch 7a is turned on, and the signal circuit 7b outputs a high-level signal. At this time, the motor
The clutch driving circuit 8b controls the mechanism member 8b to connect the clutch, and at the same time, drives the motor to return the measuring unit 3 to the reference position. When the measuring section 3 returns to the reference position, the reference position sensing means 8c outputs a signal, and the motor / clutch drive circuit 8b stops driving the motor.

As described above, when the subject places his / her face on the subject fixing unit 4 at the start of the measurement, the measuring unit 3 is at the reference position, and the examiner focuses the image reflected on the monitor 3a. The operation can be started without pushing out the measuring unit 3 without making a judgment. Further, it is possible to eliminate a feeling of oppression caused by the measurement unit 3 approaching the subject fixing unit 4.

Next, an optical system of the eye axial length measuring apparatus 1 having such a configuration will be described with reference to FIGS.

FIG. 2 is an optical explanatory view of an eye axial length measuring apparatus according to the present invention. In FIG. 2, the optical system provided in the measuring unit 3 includes an illumination system, a reference system, a fundus reflection light receiving system,
It comprises a fundus distance measuring optical system 100 sharing a reference light receiving system and a reference interference system, and a corneal distance measuring optical system 200.

The illumination system includes a measurement light irradiation optical system 110, a first optical system 120, and a second optical system 130. The reference optical system includes a first optical system 120 and a third optical system 140. The system includes a second optical system 130 and an interference optical system 150, and the reference light receiving system includes a third optical system 140 and an interference optical system 1.
50, and the reference interference system includes a measurement light irradiation optical system 110 and a reference interference optical system 160.

The measurement light irradiating optical system 110 irradiates coherent light having a single wavelength and whose wavelength can be changed toward the eye E to be examined, and a light source 111 for emitting this coherent light.
And a collimator lens 112 for collimating the coherent light emitted from the light source 111, and an optical isolator 113 for preventing reflected light from the optical system from returning to the light source 111, and emits measurement light.

The first optical system 120 includes a condenser lens 121 and a spatial filter 122, and the measurement light irradiation optical system 11
The measurement light incident from 0 is guided to the beam splitter 9 through the condenser lens 121 and the spatial filter 122.

The second optical system 130 corrects the refractive power of the eye and irradiates the fundus Er of the eye E with measurement light with the fundus Er.
And a collimator 131, a refractive power correction lens 132, a dichroic mirror 133, and an objective lens 134. The collimator 122 and the refractive power correction lens 13
2. The light is condensed on the fundus Er via the dichroic mirror 133, the objective lens 134, and the pupil of the eye to be examined, and the light reflected from the fundus Er is guided to the beam splitter 9 again.

The third optical system 140 includes a collimator 141 and a reflection surface 142, and transmits the illumination light guided to the first optical system 120 and transmitted through the beam splitter 9 to the collimator 141.
Then, the light is reflected by the reflection surface 142 and guided to the beam splitter 9 again.

The interference optical system 150 includes a stop 151, a lens 152, and a light receiver 153. The fundus reflection light from the second optical system 130 reflected on the fundus Er and the third optical system 140 reflected on the reflection surface 142. Are combined by the beam splitter 9 and are received by the light receiver 153 while causing interference by removing reflected light other than fundus reflection and reference surface reflection. The lens 152 is used to focus the interference light that has passed through the stop 151 on the light receiver 153.

The reference interference optical system 160 has a reference optical path as a reference length. After the measurement light from the measurement light irradiation optical system 110 is split by the beam splitter 161,
The light is further split by the beam splitter 162 and sent to total reflection mirrors 163 and 164 disposed at positions separated from the beam splitter 162 by optical path lengths L2 and L1, respectively.

Then, the respective reflected lights reflected by the total reflection mirrors 163 and 164 are combined again by the beam splitter 162 and received by the light receiver 165 while causing interference with each other. Output the received light signal.

The interference light received by the light receiver 153 is
It has a phase difference twice as large as the difference between the optical path length Lt from the beam splitter 9 to the fundus Er and the optical path length Lr from the beam splitter 9 to the reflection surface 142.

Here, when the wavelength of the measurement light emitted from the light source 111 is changed within a certain range and the light reception signals of the light receivers 153 and 165 are processed according to the following principle, the reflection surface 1
The distance (Lt−Lr) from the reference plane Y (see FIG. 13) formed by the reference numeral 42 to the fundus Er can be measured. Hereinafter, the principle will be described.

Now, from the beam splitter 9 to the second optical system 1
The light flux Lt which is guided to the fundus Er by the light source 30 and is reflected by the fundus Er and is again guided to the beam splitter 9 is guided from the beam splitter 9 to the reflection surface 142 by the third optical system 140 and reflected by the reflection surface 142. An optical path difference between the light flux Lr and the light flux Lr guided to the beam splitter 9 again (referred to as a measurement optical path) is a distance (L) from the reference plane Y formed by the reference plane to the fundus Er.
t-Lr).

The optical path difference between the reference optical path from the beam splitter 162 of the reference interference optical system 160 to the total reflection mirror 164 and the reference optical path from the beam splitter 162 to the total reflection mirror 153 is L = 2 (L1−L2), and the illumination light If the wavelength λ and the amount of change in wavelength are Δλ (L is constant), the initial phase difference at the light receiver 165 is 2π (L / λ), and the phase difference after the wavelength change is 2 · π ｛L / (λ + Δλ). The phase difference is 2π (L / λ) by continuously changing the wavelength.
From 2π {L / (λ + Δλ)}.

Here, if λ >> Δλ, the phase difference after the wavelength change can be expressed as 2π (L / λ−LΔλ / λ ² ), and the change in the phase difference becomes 2π (LΔλ / λ ² ). As a result, the intensity of interference fringes observed by the light receiver 165 changes periodically. Similarly, in the optical receiver 153, the change in the phase difference is 2π.
{2 (Lt−Lr) Δλ / λ ² }, and the photodetector 153
The intensity observed at changes. Then, the optical path length Lt-Lr is calculated from the signals having the intensity that changes periodically.

Here, assuming that a change in the phase difference at the light receiver 153 is φ1 and a change at the light receiver 165 is φ2, φ1 = 2π ｛2 (Lt−Lr) Δλ / λ ² ｝ (A) φ2 = 2π (L · Δλ / λ ² ) (B) From these, when Δλ / λ ² is eliminated, Lt−Lr = L · φ1 / 2φ2 (C), and the signals obtained by the photodetectors 153 and 165 are obtained. Lt−Lr can be calculated by calculating the change amount of each phase difference from L (L is known).

Next, how the wavelength is changed and the obtained signal is processed will be described.

As the light source 111, a semiconductor laser (LD) whose wavelength can be changed at a single wavelength is used. The light source 111 is pulse-shaped using a rectangular wave input by the drive circuit 181 (FIG. 3).
(Refer to (a)) ON / OFF. Light source 111
When is turned on, it takes time for the temperature inside the chip to reach equilibrium. The oscillation wavelength of the light source 111 changes when the temperature of the chip changes, and the relationship between the temperature and the wavelength corresponds one-to-one except at the position of the mode hop. That is,
When the light source 111 is turned on, a chip temperature change occurs,
Accompanying this is a change in the wavelength of the emitted light.

As shown in FIG. 3 (b), the change in temperature is abrupt immediately after the start of oscillation, and gradually converges. After a certain time, the light source 111 is turned off to return the temperature to the original state, and the irradiation is stopped. If the pulse width is properly selected, the reproducibility of the wavelength change can be obtained.

For example, the light source 111 at a speed of about 1 KHz
When the is driven in a rectangular shape, the main part of the wavelength change can be used and there is also reproducibility.

A light source 111 having a mode hop interval wider than this change width is used. The reference temperature of the light source 111, that is, the reference wavelength is shown in FIG. 4 so that mode hop does not occur during the temperature change during the pulse period. It is controlled by a drive control circuit 11 with a Peltier element not shown. That is, the reference wavelength of the laser beam is controlled.

In response to this temperature change, there is a change in the oscillation output (there is a transitional period until the output is stabilized when a rectangular input is applied and turned on.
(Omitted in (a)) converges very quickly, so it can be said that there is almost no change in intensity during the pulse period (thus, it is actually used after the transition period).

However, the change in the wavelength at this time is not linear, but changes greatly at first, and the amount of change gradually decreases. Thus, the frequency of the resulting signal is very high initially and gradually decreases over time.

As can be seen from FIGS. 3C and 3D, the light receiving signals S1 and S2 output from the light receivers 153 and 155
Is also high in the initial period, and gradually decreases with time.

Therefore, the signal S shown in FIGS.
A / D using 1 and S2 as they are using a fixed frequency trigger
If the A / D conversion is performed by the converter 14 and the data is converted into data, the signal is recorded as a signal whose frequency is high in the initial period and gradually decreases with the passage of time. Cannot be calculated.

Now, when the equation (C) is modified, 2 (Lt−Lr) / L = φ1 / φ2 (D)

This means that the ratio of the phase difference change between the reference optical path and the measurement optical path is the same as the optical path difference ratio. In other words, when the wavelength changes by a certain amount, the change in the phase difference is proportional to the optical path difference.
Is compared with the signal on the measurement optical path (the signal from the photodetector 153), at the same time, the ratio of the phase difference change is always the ratio of the optical path difference.

This is true no matter how the wavelength of the light source 111 is continuous. Therefore, if the optical path difference of the reference optical path is made sufficiently long with respect to the measurement optical path, and the interference signal from the reference optical path is used as a trigger signal to sample the interference signal of the measurement optical path, and the sampled data is arranged in order, the apparent A signal with an equal period is obtained.

That is, one trigger signal is generated for each cycle of the interference signal from the reference optical path, and the measurement signal is sampled and written in the memory 16 by this trigger signal. It means to think by replacing with memory address. Since the ratio between the measurement signal cycle and the trigger cycle is constant, the signal on the memory is an equal cycle signal. Thus, the signal is stored in the memory 16 for each pulse.

Next, periodic analysis is performed from the stored data. Since an actual signal contains electrical noise, random noise is removed by averaging a plurality of pulses, for example, 128 pulses. Perform periodic analysis.

Since the period T obtained here means the number of triggers corresponding to one period of the measurement signal, that is, the ratio φ1 / φ2, Lt-Lr can be immediately obtained from the equation (D).
Actually, signals due to light reflected from different reflecting surfaces inside the eyeball are also carried, so that they are selected during period analysis.

FIG. 4 shows the optical path length Lt− by the above method.
FIG. 3 is a block diagram showing a configuration of a signal processing circuit for obtaining Lr.

The configuration and operation will be described below with reference to the waveforms shown in FIG.

In FIG. 4, reference numeral 11 denotes a drive control circuit that supplies a pulse current to the light source 111 to drive the light source 111 and controls the temperature of the light source 111 chip by a Peltier effect element (not shown). Light receiving signal S2 output from the amplifier 165 via the amplifier 13
The trigger signal Sg is output as shown in FIG. The light receiving signal S1 output from the light receiver 153 via the amplifier 15 is converted into the A / D converter 1 at the timing of the trigger signal Sg output from the trigger circuit 12.
4 performs A / D conversion.

Reference numeral 16 denotes a memory for storing the digital value A / D converted by the A / D converter 14;
As shown in (f), a digital value corresponding to the amplitude value of the signal S1 is stored.

Then, the arithmetic and control unit 18 performs a period analysis based on the data stored in the memory 16 and
From this period T, the optical path length Lt-L is calculated by the equation (D).
Calculate r.

On the other hand, the corneal distance measuring optical system 200 includes a ring illumination 201 (a ring-shaped illumination light irradiation unit) and a first optical path 2.
10 and a second optical path 220.

The ring illumination 201 projects a ring-shaped illumination light whose parallel section is a meridional section to the eye to be inspected. With such illumination, a ring-shaped opposite image (virtual image) I is formed on the cornea Ec of the eye E to be examined. The corneal illumination light and the fundus illumination light for fundus distance measurement change the wavelength range used,
The light is separated by a dichroic mirror 133.

The corneal illumination light is transmitted, and the fundus illumination light is reflected. The light reflected by the cornea Ec is guided to the half mirror 202 via the objective lens 134 and the dichroic mirror 133, and is branched into the first optical path 210 and the second optical path 220.

The first optical path 210 is connected to the objective lens 13
4. Dichroic mirror 133, half mirror 20
2, lens 211, mirror 212, lens 213, aperture 214, half mirror 203, imaging lens 204, beam splitter 205, two-dimensional image sensor (two-dimensional light receiving element)
Child) 206 is provided.

The second optical path 220 is connected to the objective lens 13
4. Dichroic mirror 133, half mirror 20
2, mirrors 221, 222, lens 223, mirror 22
4, a stop 225, a beam splitter 205, and a two-dimensional image sensor 206.

The reflected light guided to the first optical path 210 passes through the dichroic mirror 133 and passes through the half mirror 202
After being reflected by the lens 211 and once formed as a ring-shaped aerial image Ia by the lens 211, the mirror 212 and the lens 21
3. Aperture 214, half mirror 203, imaging lens 20
4 and is formed on the two-dimensional image sensor 206 as a ring image I2 (see FIG. 5). Here, this ring image I
The imaging magnification of No. 2 is 0.5 times.

The reflected light guided to the second optical path 220 passes through the dichroic mirror 133 and the half mirror 202, is reflected by the mirror 221 and once forms an aerial image Ib as an image by the objective lens 134, and further, the mirror 2
22, a lens 223, a mirror 224, an aperture 225, a half mirror 203, an imaging lens 204, and a ring image I1 on a two-dimensional image sensor 206 via a beam splitter 205.
(See FIG. 5). Note that this ring image I
The imaging magnification of 1 is set to be larger than the imaging magnification of the ring image I2. The two-dimensional image sensor 206 captures these ring images I1 and I2.

It is desirable that the ring images I1 and I2 be concentrically formed on the two-dimensional image sensor 206 as shown in FIG. This is because when the ring images I1 and I2 are eccentric, correction can be made in some cases, but, for example, when the ring image I2 is displaced to the periphery of the two-dimensional imaging element 206, aberrations at the lens peripheral portion cause This is because a distortion or the like occurs and a measurement error increases.

Also, depending on the subject, the eyelids may fall down and appear, and in this case, the ring images I1 and I2 cannot be detected accurately, which may lead to an incorrect calculation.

Therefore, a part of the ring images I1 and I2 is received in a plane conjugate with the two-dimensional
A check light receiving unit 207 is provided, which can measure an image formation state of the two-dimensional imaging device 206 at 1 and I2 while checking in real time.

The check image pickup unit 207 is provided as shown in FIG.
As shown in (a), a part of the ring images I1 and I2 reflected by the beam splitter 205 is received.
Four one-dimensional light receiving elements 231, 232, 233, 2 installed radially and uniformly around an axis A that is coaxial with the optical axis O
34.

The one-dimensional light receiving elements 231, 232, 233,
Reference numeral 234 denotes a one-dimensional image sensor or a one-dimensional position detecting element. When the ring images I1 and I2 are located concentrically, the axis A and the centers of the ring images I1 and I2 overlap each other, and FIG. As shown in (b), each one-dimensional light receiving element 2
The ring image I1, is uniformly distributed on 31, 32, 233, and 234.
It is set so that a part (indicated by the same reference numeral) of I2 is received. If necessary, the ring images I1 and I2 may be enlarged / reduced via a lens and then received.

As shown in FIG. 7A, when the ring images I1 and I2 formed by the corneal reflected light are present as the opposite image I behind the cornea Ec, for example, as shown in FIG.
When the eye E is slightly shifted downward with respect to the optical axis O (indicated by the corneal curvature center Co), the position of the opposite image I is similarly shifted downward. Due to this shift, as shown in FIG. 8 (a), the ring images I1 and I2 are also received by the check light receiving unit 207 in a state shifted downward.

The first and second optical paths 21 having different magnifications
Since the ring images I1 and I2 are observed at 0 and 220, the amount of movement of the ring images I1 and I2 due to the above-described displacement differs depending on the magnification. In this case, the outer ring image I2
8 has a larger observation magnification, and as shown in FIG. 8A, the amount of movement of the ring image I2 is larger than that of the ring image I1 and moves downward in the figure. As a result, as shown in FIG. Thus, each one-dimensional light receiving element 231, 232, 233, 2
The light-receiving positions of the ring images I1 and I2 and the light-receiving intervals of the ring images I1 and I2 are greatly different from each other.

As shown in FIG. 9A, when the eyelid image M overlaps the ring images I1 and I2 formed by the corneal reflected light, as shown in FIG. the original received
Since the light receiving portion of the optical element 231 receives a large amount of light outside (to the right in the figure), the other one-dimensional light receiving elements 232 and 23
The light receiving state is significantly different from 3,234
Can be instantaneously detected.

The stop 214 serves as a second stop, is relayed by the lenses 213 and 211 to the rear focal position of the objective lens 134, a conjugate image 214 'is formed at that position, and the optical system of the first optical path 210 is Telecentric on the object side. The stop 225 functions as a first stop, and is relayed by the lens 223 in front of the subject's eye E (in front of the objective lens 134).
5 ′ is formed at a position 25 to 50 mm in front of the eye E to be examined.

Next, the objective lens 134 and the apertures 214 and 2
The relationship with 25 will be described with reference to FIGS. 10 and 11 schematically show the second optical path 220 and the first optical path 210, respectively.

Now, with the position on the optical axis O where the conjugate image 225 'of the stop 225 is formed as the origin G, a reference position Ya is determined at a position separated from the origin G by the distance La in the optical axis direction. This reference position Ya is determined at a position where neither the ring images I1 nor I2 is out of focus. And this reference position Ya
An object having an object height h (corresponding to the radius of the ring image I) is placed on the. At this time, the image height formed on the observation surface 240 (the position of the two-dimensional image sensor 206) by the second optical path 220 is y1,
The image height formed on the observation surface 240 by the first optical path 210 is defined as y2.

Next, image heights when this known object is moved by the distance X0 are defined as y1 'and y2'. Further, the distance from the observation surface 240 to the point Z is La ′, the distance from the reference position Ya to Z ′ is Lb, and the distance from the stop 214 ′ to the observation surface 240 is
The distance up to Lb ′ is defined as Lb ′. Further, the angular magnifications of the first and second optical paths by the objective lens 134 are β1 and β2.

Then, the following equation is obtained.

H / La = (y1 · β1) / La ′ (1) h / (La + X0) = (y1 ′ · β1) / La ′ (2) h / Lb = y2 / (β2 · Lb) ') (3) h / (Lb + X0) = y2' / (β2 · Lb ') (4) In the equations (1) and (2), the angular magnification β1 and the distance L
If a and La ′ are constants and K1 = (β1 · La) / La ′ K2 = β1 / La ′, the equations (1) and (2) are transformed into the following equations.

H = K1 · y1 (5) h = K1 · y1 ′ + K2 · y1 ′ · X0 (6) Further, in equations (3) and (4), the angular magnification β2 and the distance L
Assuming that b and Lb ′ are constants and K3 = Lb / (β2 · Lb ′) K4 = 1 / (β2 · Lb ′), the expressions (3) and (4) are given by h = K3 · y2. (7) h = K3 · y2 ′ + K4 · y2 ′ · X0 (8)

Here, the constants K1, K2, K3, K4 are:
It can be determined by actually measuring the object height h and the image height y.

That is, the following equations are obtained by modifying the equations (5) and (6).

K1 = h / y1 (9) K2 = (h / y1) (y1-y1 ′) / (y1 ′ · X0) (10) K3 = h / y2 (11) K4 = (H / y2) (y2-y2 ') / (y2'.X0) (12) Thus, by actually measuring the object height h and the image height of a known object, the constants K1, K2, K3, Find K4.

Next, measurement when the object height h and the distance X from the reference position Ya are unknown distances will be described.

In this case, the distance X is used instead of the distance X0 in the equations (2) and (4). Also, y1 ',
Replace y2 'with y1 and y2.

Then, the following equation is obtained.

H = K1 · y1 + K2 · y1 · X (14) h = K3 · y2 + K4 · y2 · X (15) When the above simultaneous equations are solved for the distance X and the object height h, X = ( K3 · y2−K1 · y1) / (K2 · y1−K4 · y2) (16) h = K1 · y1 + K2 · y1 · X = (K2 · K3−K1 · K4) y1 · y2 / (K2 · y1) −K4 · y2) (17) Since K1 to K4 have been determined, the distance from the reference position Ya to the object can be measured by measuring the image heights y1 and y2.

Next, the measurement of the corneal curvature radius R and its vertex position will be described with reference to FIG.

In FIG. 12, the radius of the ring image I (the major axis or minor axis of the ellipse when the ellipse is approximated) is defined as the object height h. At this time, the object height h is determined by the meridional ray. If the diameter of the ring image is about 3 mm,
The angle φ is about 20 °, and the following paraxial formula cannot be used.

H = (R · sin φ) / 2 Then, the distance L2 is set to be sufficiently large so that the angle φ is always constant, and the object height h is measured on the second optical path 220 passing through the stop 225. Is used, an equation based on the following reflection law can be used.

H = R · sin (φ / 2) If this is modified, then r = h / sin (φ / 2) (18), so that the ray passing through the stop 214 and the ray passing through the stop 225 become If the distance L1 is set so as not to increase the angle to be performed, the object height h obtained by the equation (17) becomes (1)
Since it is considered that there is no big error even if it is used for the expression 8),
The position of the corneal vertex Ep is Px = X− (r−h / tanφ) (19) as the distance Px from the reference position Ya.

The equation (19) for calculating the corneal apex position is affected by the spherical aberration since the ring image is on the optical axis of the spherical surface, and may be corrected based on the experimental value. . Therefore, the distance Px can be obtained from the diameters of the ring images I1 and I2 formed on the two-dimensional image sensor 206.

This calculation is based on the two-dimensional image sensor 206
The data of the ring images I1 and I2 formed in the frame memory 17 are stored in the frame memory 17, and the operation is performed by the arithmetic and control unit 18 based on the data in the frame memory 17. The image output data from the arithmetic processing circuit 18 is output to the monitor switching circuit 19.

In FIG. 12, A1 and A2 are normals of the spherical surface when the cornea Ec is regarded as a spherical surface, and A3 is a normal of the cornea Ec.
c is a ray of light incident on c.

Then, the one-dimensional light receiving elements 231, 232,
A part of the ring images I1 and I2 received by the light sources 233 and 234 are output to a signal processing circuit 21 via a frame memory 20, and the signal processing circuit 21
07, the light receiving state of the ring images I1 and I2 is determined.

For example, when the ring images I1 and I2 are received while the eye E is in a normal state, the one-dimensional light receiving elements 23
1, 232, 233, 234 closer to axis A (FIG. 6
The signal data having a waveform having a constant signal interval as shown in FIG.
Is output to the signal processing circuit 21 by the signal data.
Judge that the light receiving state of the ring images I1 and I2 is normal.

Further, when the eye E is shifted, the ring image I
When I 1 and I 2 are received, for example, when they are shifted downward as shown in FIG.
Signal data having a waveform as shown in FIG. 8C is output to the signal processing circuit 21 from 31, 32, 233, and 234.
Based on this difference in the signal data, the signal processing circuit 21 determines that the ring images I1 and I2 are shifted downward.

Note that the difference between the signal data is the one-dimensional light receiving element 2
Combination of 31, 234 and one-dimensional light receiving element 232, 2
By comparing the combinations of the 33 combinations, the directions of up, down, left, and right displacements can be detected.

Further, when the eyelid image M is received simultaneously, the one-dimensional light receiving elements 231, 232, 233, 23
4 to 9 (c) are output to the signal processing circuit 21. The difference between the signal data is
The signal processing circuit 21 determines that the upper eyelid of the subject is received in addition to the ring images I1 and I2.

As described above, after the light receiving state of the ring images I1 and I2 is determined by the signal processing circuit 21, the image output data is output to the monitor switching circuit 19, and the two-dimensional image pickup device Either the image output data 206 or the image output data of the check light receiving unit 207 is output to the monitor 3a.

When the light receiving states of the ring images I1 and I2 are not normal, alignment correction data is output from the signal processing circuit 21 to the alignment correction means 22.

The alignment correction means 22 calculates the alignment correction data from the signal processing circuit 21 from the difference due to the combination of the one-dimensional light receiving elements 231, 232, 233, 234 described above, and measures the alignment in the direction to correct this difference. 3 to control the motor / clutch drive circuit 8b.

The signal processing circuit 21 generates the ring images I1,
As a result of judging the alignment state based on the light receiving state of I2, if the alignment is not OK, the photographing device (not shown) is locked so that the photographing is not performed, or a warning is issued to the examiner. It is also possible to configure so that

FIG. 13 shows the relationship between the fundus distance, the corneal vertex distance, and the axial length determined in this way, and shows the case where the above-described reference position Ya matches the reference plane Y.

Then, Lt-Lr obtained by the interferometry
By subtracting Px, a value Leye obtained by converting the axial length of the eye into air is obtained. If the reference position Ya does not coincide with the interference reference plane 10, the difference may be obtained in advance and corrected at the time of calculation. Once Leye is obtained, the axial length can be calculated by dividing this by the average refractive index of the eyeball. These calculations are also performed by the calculation control device 18.

Since the focal position of the corneal reflected light substantially coincides with the anterior segment, an anterior segment illumination (not shown) is provided, and a two-dimensional image of the anterior segment as well as the reflection ring image formed by the corneal reflected light is provided. The image is captured by the element 206 and the monitor 3a (or
It is observed by another display (not shown) or printed by a printer (not shown).

By the way, the check light receiving unit 207 is set so that there is no difference between the signals when the ring images I1 and I2 are concentric. However, in the case of a double ring, the light is photographed concentrically. Is important. In this case, it is sufficient to check the interval between rectangular or pulse-like signals based on the ring image.
The arrangement setting of 233 and 234 is not always necessary. When the ring image is single, it is desirable that the distance from the optical axis to the light receiving units of the one-dimensional light receiving elements 231, 232, 233, and 234 be equal. Further, when the signal interval is a problem, the absolute coordinates on the one-dimensional light receiving elements 231, 232, 233, and 234 of the ring images I1 and I2 have no meaning.

The one-dimensional light receiving elements 231, 232, 2
It is also possible to detect the contrast and frequency of the signals 33 and 234, check the focus of the ring images I1 and I2, and make the same correction as the alignment.

Further, by devising the signal processing circuit 21, the number of the one-dimensional light receiving elements 231, 232, 233, 234 can be set arbitrarily, and the ring image I1,
The present invention can be applied to a case in which I2 is not double and a single ring image is used as in an eye measurement apparatus such as a corneal curvature measurement apparatus.

In this case, the one-dimensional position detecting element (PSD =
It is also possible to use Position Sensitive Detector), and the output signal can be obtained as a signal that represents the coordinates on the element where the ring image is in contact with the intensity, so by comparing the output signal intensities Can be detected.

(Embodiment 2) The eye measuring apparatus according to the present invention is not limited to the optical system of the eye axial length measuring apparatus 1 shown in the above embodiment, and is, for example, shown in FIG. Also, the present invention can be applied to an optical system of an eye axial length measuring device.

The optical system of the eye axial length measuring device shown in FIG. 14 includes an illumination optical system 300 and a corneal distance measuring optical system 200. Since the corneal distance measuring optical system 200 has the same configuration as that of the above-described embodiment, the same reference numerals are given and the description is omitted here. In the illumination optical system 300, the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The illumination optical system 300 includes a measurement optical path 310 and a reference optical path 320.

The measurement optical path 310 includes a light source 311, a lens 3
12, a pinhole 313, a beam splitter 314, a lens 315, a focusing lens 316, a total reflection mirror 317,
A dichroic mirror 133 and an objective lens 134 are provided.

The reference optical path 320 includes a lens 321, total reflection mirrors 322, 323, and 324, and a model eye unit member 3
25, a total reflection mirror 326, a pinhole 327, a lens 328, and a photosensor 329 having a point aperture.

The light source 311 is a laser diode having a low coherence length.
It is about 0.05 mm to 0.1 mm. Its wavelength is near infrared and has an antiglare effect.

Then, the laser beam emitted from the light source 311 is condensed on the pinhole 132 by the lens 131. The pinhole 132 serves as a secondary point light source. Note that an LED having a narrow spectrum width may be used as the light source 311 instead of the laser diode.

The laser beam passing through the pinhole 313 is split by the beam splitter 314 into a light beam going to the lens 315 and a light beam going to the lens 321.

The lenses 315 and 321 are pinholes 313.
It plays a role of collimating the laser light that has passed through.
The laser light collimated by the lens 315 is
A spot is formed at the focal position Q of the focusing lens 316 by the focusing lens 316.

This focal position Q is conjugated to the fundus 147 with respect to the objective lens 104. The laser beam that forms a spot at the focal position Q is guided to the eye E via the total reflection mirror 317, the dichroic mirror 133, and the objective lens 134, and forms a spot on the fundus Er. The eye E can fixate the spot image.

The pinhole 327 is provided at the focal position of the lens 315. The pinhole 327 is conjugate with the fundus Er.

The lens 316 has a function of collimating the fundus reflected light. The collimated fundus reflected light is relayed by the lens 315 via the beam splitter 314 and the total reflection mirror 326 to the pinhole 327.

The laser beam collimated by the lens 321 is guided to the model eye unit member 325 by mirrors 322, 323, and 324.

The model eye unit member 325 is movable so that the optical path length of the reference optical path and the optical path length of the measurement optical path are the same, and is roughly constituted by a lens 330, a reflection mirror 331, and a movable member 332. . Further, the model eye unit member 325 is used to eliminate the deflection of the reflected light beam due to the blur caused by the movement thereof, and may be a simple movable mirror in principle.

The fundus reflection light and the reference light are transmitted through the pinhole 32
The light flux condensed on 7 and passed through the pinhole 327 is converged on the photosensor 329 by the lens 328. When the model eye unit member 325 is moved, an interference waveform is obtained only in a range where the optical path difference between the reference optical path and the measurement optical path is about the coherent length of the light source 311. This interference waveform changes sinusoidally each time the optical path length changes by one wavelength, and the amplitude is largest when the optical path difference is zero. Thereby, the distance from the apparatus optical system to the fundus Er is measured, and the axial length of the eye is determined based on the position from the apparatus optical system to the corneal vertex Ep and the position from the apparatus optical system to the fundus Er.

[0127]

As described above, in the eye measuring apparatus of the present invention , ring-shaped illumination light is applied to the cornea of the eye to be inspected.
A ring-shaped illumination light irradiating section for irradiating, and a corneal surface of the illumination light
The ring-shaped opposite image formed by the
A light receiving optical system for forming a number of ring images;
A plurality of rings arranged radially around an optical axis orthogonal to the conjugate plane on a conjugate plane substantially conjugate to an imaging plane of the plurality of ring images formed in a scientific system and obtained at different magnifications;
A plurality of one-dimensional light receiving elements for receiving images; and a signal processing circuit for determining whether or not the plurality of ring images are in an appropriate state based on output signals from the respective one-dimensional light receiving elements are provided. By doing so, it is possible to check whether the ring image is at a predetermined position or not, and whether or not there is reflection of an eyelid image at a speed close to real time.

[Brief description of the drawings]

1A and 1B show an eye-to-be-measured measuring apparatus of the present invention, in which FIG. 1A is a side view of an eye axial length measuring apparatus showing an embodiment of the present invention, and FIG.
Is a block diagram.

FIG. 2 is an explanatory diagram of an optical system of the eye axial length measuring device.

FIG. 3 is an explanatory diagram showing signal waveforms and the like output from each circuit of a control system.

FIG. 4 is a block diagram showing a configuration of a control system for calculating an axial length.

FIG. 5 is an explanatory diagram showing a ring image formed on a light receiving surface of a two-dimensional image sensor.

FIG. 6A is an explanatory view showing a ring image in an appropriate state formed on each light receiving surface of a one-dimensional light receiving element, and FIG.
7A and 7B are explanatory diagrams for comparing the light receiving states of the one-dimensional light receiving elements in parallel, and FIG. 7C is an explanatory diagram for comparing the signals from the one-dimensional light receiving elements shown in FIG.

FIG. 7A is a diagram illustrating a state in which ring-shaped illumination light is applied to an appropriate position of an eye to be inspected, and FIG. 7B illustrates a state in which ring-shaped illumination light is applied to a position shifted to the eye to be inspected; FIG.

8 (a) is an explanatory view showing the ring images of improper state formed on the light receiving surface of the one-dimensional image sensor, (b) is received in parallel each one-dimensional light receiving element (a) FIG. 3C is an explanatory diagram comparing states, and FIG. 3C is an explanatory diagram comparing signals from the one-dimensional light receiving elements shown in FIG.

9A is an explanatory diagram showing a state in which an eyelid image is superimposed on a ring image in an appropriate state formed on each light receiving surface of a one-dimensional light receiving element, and FIG. FIG. 7C is an explanatory diagram in which light receiving elements are arranged in parallel and light receiving states are compared, and FIG. 7C is an explanatory diagram in which signals from the one-dimensional light receiving elements shown in FIG.

FIG. 10 is an explanatory diagram schematically showing a stop of a second optical path and an objective lens of the corneal distance measuring optical system.

FIG. 11 is an explanatory view schematically showing a stop of a first optical path and an objective lens of the corneal distance measuring optical system.

FIG. 12 is an explanatory diagram illustrating measurement of a corneal curvature radius and a vertex position thereof.

FIG. 13 is an explanatory diagram showing a relationship between a fundus distance, a corneal vertex distance, and an axial length.

FIG. 14 is an explanatory diagram of an optical system of an eye axial length measuring apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

21: signal processing circuit 200: corneal distance measuring optical system ( light receiving optical system) 201: ring illumination (ring-shaped illumination light irradiation unit) 206: two-dimensional image receiving element (imaging plane / two-dimensional light receiving element ) 207: check Light receiving unit 231 ... one-dimensional light receiving element 232 ... one-dimensional light receiving element 233 ... one-dimensional light receiving element 234 ... one-dimensional light receiving element A ... axis E ... eye to be examined Ec ... cornea I ... opposite image I1 ... ring image I2 ... ring image

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) A61B 3/00-3/16

Claims (3)

(57) [Claims] 1. A ring-shaped illumination light irradiating unit that irradiates a ring-shaped illumination light to a cornea of an eye to be inspected, and a plurality of ring-shaped opposite images formed by corneal reflection of the illumination light having a plurality of magnifications different from each other.
A light receiving optical system for forming a ring image, and the light receiving optical system
The plurality of ring images are radially arranged around an optical axis orthogonal to the conjugate plane on a conjugate plane substantially conjugate to the image plane of the plurality of ring images formed at and obtained at different magnifications.
A plurality of one-dimensional light receiving elements for receiving light; and a signal processing circuit for determining whether or not the plurality of ring images are in an appropriate state based on an output signal from each one-dimensional light receiving element. An eye measurement apparatus characterized in that: 2. The signal processing circuit according to claim 1, wherein each of the one-dimensional light receiving elements is
Said complex obtained at different magnifications in the output signal from the
The plurality of ring images based on the light receiving positions of the number of ring images
To determine whether or not is in a proper state
The eye measurement device according to claim 1. 3. The image forming surface is formed by the light receiving optical system.
Two-dimensional light receiving element that receives multiple ring images of different magnifications
And the signal processing circuit is an output of the two-dimensional light receiving element.
Determines corneal vertex position based on force
The eye measurement device according to claim 1.