JP3459685B2 - Ophthalmic 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 an ophthalmologic measuring device.

[0002]

2. Description of the Related Art Conventionally, in an ophthalmic measuring apparatus, a precise optical system is arranged inside. For this reason, once the device is assembled, internal components may undergo thermal deformation or optical system changes due to the operating environment such as temperature and humidity of the user who actually uses the device, or the internal temperature rising due to long-time energization of the device. There is a possibility that a slight displacement of the arrangement may occur, which may appear as an error in the measured value. In order to prevent or reduce such an error in the measured value, a material with a small coefficient of thermal expansion is used as a component, or a fixing method that reduces the thermal stress applied to the optical component, such as elasticity like a spring. It was fixed with a member that has a property. Alternatively, it is known that a temperature sensor is installed inside the device, the temperature inside the device is detected at the time of measurement, and the measured value is corrected by the detection result.

[0003]

However, in the conventional example in which the error of the measurement value due to the temperature change is suppressed by using the material having a small coefficient of thermal expansion or devising the fixing method of the optical component, the optical component is fixed. There have been problems that the parts are complicated, the number of parts is large, and expensive materials are required for the materials of the parts including the optical parts, resulting in high cost. Even if such components are used or fixed, the thermal stress applied to the optical components will vary due to variations in component manufacturing and assembly, and the expected variation in measured values will be within tolerance. There was a danger that some devices would not fit inside.

Further, in the conventional example in which a temperature sensor is installed inside the apparatus and the measured value is corrected by the detected temperature,
High cost has come because expensive components such as a temperature sensor and related control circuits are used. Also, with such a temperature sensor, the temperature is usually measured at one point, so there is no guarantee that the temperature change at the measurement point will be a uniform temperature change of the entire device and optical system due to the ambient temperature, and the power to the device will not be applied. When a partial temperature change occurs due to, the correction of the measured value cannot be uniquely determined only by the temperature detected by the temperature sensor, and the accuracy of the measured value may not be maintained.

A first object of the present invention is to eliminate errors in measured values without incurring high costs for optical system parts, fixing methods, temperature sensors and the like, and also due to fluctuations in the optical system due to environmental changes such as temperature changes. An object of the present invention is to provide a highly accurate ophthalmologic measuring device capable of preventing occurrence.

A second object of the present invention is to provide a highly accurate ophthalmologic measuring apparatus capable of preventing the occurrence of an error in the measured value due to any change in the optical members of the measuring optical system due to environmental changes.

A third object of the present invention is to provide a more highly accurate ophthalmologic measuring apparatus in which the influence of fluctuations due to temperature changes of the compensating projection system itself is reduced.

A fourth object of the present invention is to provide a highly accurate ophthalmologic measuring device in which the decrease of the measuring light quantity caused by guiding the compensating light beam to the measuring optical system is suppressed.

A fifth object of the present invention is to provide a highly accurate ophthalmologic measuring device which can guide the compensating light beam to the measuring optical system without using the wavelength difference which causes the problem of chromatic aberration. .

A sixth object of the present invention is that the result of light detection of the corneal reflection image and the light beam from the compensating projection system can be processed by a similar arithmetic processing circuit or program, thereby facilitating the construction and high precision. To provide a simple ophthalmic measuring device.

[0011]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a measurement projection system for projecting a measurement target onto an eye to be inspected, and a light detection of reflected light from the eye to be inspected of the light flux for measurement. A measuring optical system projecting onto the means, and a calculating means for calculating the eye characteristic of the eye to be examined based on the detection of reflected light of the photodetector, wherein the measuring optical system includes an optical path synthesizing member. A compensation projection system for projecting an optotype of substantially the same shape as the measurement optotype to the photodetector through at least a part of the system, and a reflection image formation in which a reflection image from the measurement site of the subject's eye is formed. Position and a compensating target disposed at a position substantially equivalent to the optical path synthesizing member, and storage means for storing reference image data of the compensating target, and the compensating light flux detection by the photodetector. The calculation using the result and the image data stored in the storage means An ophthalmic measurement apparatus, characterized in that to compensate for the eye characteristic measurement value by stages.

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

1 is a block diagram of a corneal shape measuring apparatus according to a first embodiment of the present invention.

In the figure, reference numeral 1 is a measuring unit of the apparatus, and an examiner aligns the eye E with the measuring unit 1 by a positioning operation means such as a joystick (not shown).

[0019] 2 is an index for corneal shape measurement is projected onto the cornea E _C of the eye E, the measurement optical axis O ₁ as shown in FIG. 2
It is a ring-shaped light source centered on. The light source for measurement is arranged around the objective lens 3 so as to face the eye E to be inspected, emits light of a predetermined wavelength, for example, λ = 780 nm, and a ring-shaped index is formed on the eye cornea E _C to be inspected. To project. In this embodiment, the measuring light source is also used as an index for aligning the eye to be inspected.

Reference numeral 4 is a light splitting member, 5 is a lens system, 6 is light detecting means, 7 is a diaphragm, 8 is a rotation axis of the diaphragm, 9 is control means,
Reference numeral 10 is a storage means, 11 is a display means such as a monitor, 12 is a compensation index described later, and 13 is a light source.

When aligning the eye E to be inspected, the light source 2 for measurement is turned on, and the light flux reflected by the cornea E _{C of the} eye to be inspected is passed through the lens 3, the light splitting member 4, and the lens system 5 to the light beam. An image is formed on the image pickup device of the detection means 6. here,
The light detecting means 6 is a two-dimensional image pickup device such as a so-called two-dimensional CCD. A display unit 11 is connected to the light detection unit 6 so that an anterior segment image of the eye E can be displayed when the eye E is aligned. The examiner receives the image pickup signal from the light detection means 6 and looks at the corneal reflection image of the ring-shaped measurement index 2 displayed on the display means 11,
The position of the measuring unit 1 is operated so that the ring-shaped corneal reflection image is located at a predetermined position on the image sensor, for example, at the center, and the corneal reflection image is in focus. In this way, the measurement index 2 is used as an index for alignment during alignment.

FIG. 3 is an example of a corneal reflection image I _E of the measurement index 2 by the cornea E _C of the eye to be inspected, which is imaged by the light detecting means 6. The corneal reflection image may be a circle, an ellipse, or an indefinite shape depending on the state of the cornea E _C of the eye to be examined, for example, the state of corneal astigmatism or keratoconus. The present apparatus measures the shape of the cornea E _C of the eye to be inspected by calculating the size and shape of this corneal reflection image I _E.

In FIG. 4, the alignment of the eye E to be examined is completed,
It is a figure which shows the state of this apparatus at the time of measuring a cornea shape.
In this state, the diaphragm 7 is rotated around the axis 8 and inserted in the optical path of the measuring optical system. In this state, the diaphragm 7 is a so-called telecentric diaphragm, and the size of the corneal reflection image does not change even if there is a positional error of the eye E to be examined in the focus direction. As shown in FIG. 5, the diaphragm 7 has an opening 7a centered on the optical axis O ₁ . The shaft 8 is attached to a rotary drive member such as a stepping motor (not shown), and the control means 9 that controls the alignment and the measurement controls the diaphragm 7 to bring the diaphragm 7 out of the measurement optical path as shown in FIG. Evacuate and place the diaphragm 7 in the measurement optical path so that it works as a telecentric diaphragm during measurement.
Drive to rotate.

The control means 9 is connected to the light detection means 6 and a storage means 10 composed of a frame memory and the like,
It also controls the following measurement controls. First, the image pickup signal of the corneal reflection image I _E obtained by the light detecting means 6 in the state where the alignment is completed is temporarily stored in the storage means 10 as video information. By using the stored image information, the control unit 9 calculates the information such as the shape and size of the corneal reflection image I _{E which} is stored while being corrected by the compensation information such as the temperature to be described later, and the cornea E of the eye to be inspected E is calculated. _It is configured to calculate the shape of _C.

The light splitting member 4 is a beam splitter such as a dichroic mirror in this embodiment, and has a wavelength of 780n.
It has an optical characteristic that light near m is transmitted and other light is reflected. In the optical path O ₂ in the reflection direction of the light splitting member 4, the compensating target 12 shown in FIG. 6 and the light source 13 for illuminating the target 12 from the rear are arranged as shown in FIGS. The light source 13 has, for example, an emission wavelength λ =
The light splitting member 4 is configured to be reflected by using an 860 nm LED or the like.

When the light source 13 is turned on, the compensation index 12 is illuminated from behind. The light flux that has passed through the index 12 is reflected by the light splitting member 4, passes through the lens system 5, and forms an image on the image pickup device of the light detection means 6 through the diaphragm 7.

FIG. 7 shows an example of an image I _C of the compensation index 12 picked up by the light detecting means 6.

Next, a specific measurement operation will be described.

After the alignment of the eye E to be inspected is completed, the examiner pushes a measurement switch (not shown) to start the measurement. When this measurement switch is pressed, the control means 9 turns on the measurement index 2, the corneal reflection image I _E by the cornea E _C of the eye to be inspected is picked up by the light detection means 6, and stored in the storage means 10, as described above. Capture as video information.

Here, in order to simplify the explanation, considering that the cornea E _{C of the} eye to be inspected is a substantially perfect spherical surface having no corneal astigmatism, the corneal reflection image I _E has a radius R as shown in FIG.
It is stored in the storage means 10 as an _E ring.

Next, the control means 9 turns off the measuring index 2,
The light source 13 is turned on and the image I _C of the compensation index 12 is projected on the image pickup device of the light detecting means 6 as described above. FIG. 9 shows an image I _C of the compensation index 12 at that time, and its radius is R _C.

The control means 9 stores the radius R _C0 of the image I _C0 of the compensation index 12 at the device temperature when the device is assembled, that is, when the measured values of the device are calibrated. This radius R _C0 is compared with the radius R _C of the image I _C of the compensation index 12 currently stored in the storage means 10, and the corneal reflection image I _E during measurement is measured in the following manner. The change in the optical system due to the temperature is corrected.

That is, the radius R _E of the corneal reflection image I _E at the time of the above-described measurement, the radius R of the image I _C of the compensation index 12 at that time
_{From C} and the radius R _C0 of the image I _C0 of the compensation index 12 during calibration, the influence of the error of the optical system due to environmental changes such as temperature between when the device is calibrated and when the actual measurement is performed The radius R _E ′ of the corrected true corneal reflection image I _E ′ can be expressed as R _E ′ = (R _C0 / R _C ) R _E. Therefore, the control unit 9 corrects the entire shape by correcting the image information of the corneal reflection image I _E stored in the storage unit 10 for each radial line based on this equation, and corrects the entire shape of the cornea. The reflected image I _E 'is analyzed by a known method to calculate the corneal shape of the eye E to be examined. Various methods are known for calculating the corneal shape of the eye to be examined by analyzing the annular corneal reflection image, and a detailed description thereof will be omitted here. Alternatively, the corneal reflection image I can be calculated by using the above equation.
The radius of _{E on} the specific radial line may be corrected, and the corneal shape of the eye E to be examined may be calculated by a known method using the radius on the specific radial line.

Even if an error factor occurs in the lens system 5 or the like in the apparatus due to environmental changes such as temperature changes, the error factor is compensated by performing the correction in this manner and performing the measurement. The shape of the cornea can be measured, and the corneal shape can be measured independently of environmental changes.

In this embodiment, in the control means 9, the image information storage means of the compensation index 12 at the time of calibration of the apparatus and the temperature correction index 12 projected on the light detecting means 6 at the time of measuring the eye to be inspected.
Correction of calculating various measured values of the corneal shape of the eye to be inspected after comparing the image information of No. 1 with the image information of the compensation index 12 stored in the storage unit in the control unit 9 and performing the above-described correction. And computing means are included.

FIG. 10 is a block diagram of a corneal shape measuring apparatus according to the second embodiment of the present invention. The same members as those in the first embodiment have the same reference numerals.

In the present embodiment, unlike the first embodiment, the light splitting member 14 is arranged as an optical member which is closer to the eye E than the lens 15 closest to the eye E, that is, facing the eye E. . The compensation index 12 and its illuminating light source 13 similar to those of the first embodiment are arranged on the optical path O ₃ in the reflection direction of the light splitting member 14. The emission wavelengths of the measurement index 2 and the light source 13 are the same as those in the first embodiment,
The optical characteristics such as the wavelength separation characteristic of the light splitting member 14 are the same as those of the light splitting member 4 of the first embodiment.

The procedure for measuring the shape of the cornea E _C of the eye to be examined is the same as that of the first embodiment, including the correction of the corneal reflection image I _E by the image I _C of the compensation index 12.

In this embodiment, the optical members after the light splitting member 14, that is, the lenses 15, 5, the diaphragm 7, the light detecting member 6 and the like are all common to the measuring optical path O ₁ and the compensating optical path. that is, by light from the compensation index 12 is through all optical components of the measuring optical path O _1, will be the error is corrected by the optical member all temperature change environmental changes in the measured optical path O _1, more Highly accurate measurement is possible.

Further, in this embodiment, the compensating optotype 12 is arranged at a position substantially equivalent to the cornea reflection image forming position by the cornea E _C of the eye to be inspected of the measuring index 2 with respect to the light dividing member 14, so that the compensating target 12 is compensated. Both the image I _{C of the} target index 12 and the corneal reflection image I _E also have the effect of reducing the influence of blurring.

In each of the above embodiments, the compensation index 12
A circular index having the same shape as that of the measurement index 2 was used for the image analysis so that the same image processing / program can be used for the corneal reflection image I _E and the compensation index image I _C. However, if different image processing / programs are used in the image analysis, as shown in FIG.
It is also possible to correct the measured value by setting 2 to, for example, 4 spots, and comparing the inter-spot distances l ₁ and l ₂ and the positional relationship of the 4 spots with the index used in the configuration.

Further, in each of the above-mentioned embodiments, the light splitting members 4 and 14 such as dichroic mirrors are used as the light path splitting members for projecting the compensation index 12 onto the light detecting means 6 through the measuring optical system. However, the index 2 for measuring the cornea E _C of the eye to be examined
It is also possible to use a movable mirror which is retracted from the measurement optical path O ₁ when the image is captured, and is inserted into the measurement optical path O ₁ when the compensation index 12 is projected onto the photodetection means 6 to capture the image. In this case, the light wavelengths of the light source 13 for illuminating the measurement index 2 and the compensation index 12 may be the same, and if the light wavelengths are the same, there is no difference in image forming position due to the wavelength of the optical system. Also,
If the movable mirror is used, the mirror is irradiated with light only when necessary, so that the influence of thermal deformation of the light splitting member is reduced and more accurate correction can be performed.

Further, in each of the above-mentioned embodiments, the example in which the present invention is applied to the corneal shape measuring apparatus is described, but it is also applicable to other ophthalmologic measuring apparatuses such as an eye refraction system. That is, in the device that receives the measurement light from the eye to be inspected and measures the eye to be inspected based on the light receiving position and the light receiving image, the compensation index is projected onto the light receiving means via at least a part of the measurement optical system, If the compensation position of the measuring light and the received image are corrected based on the position of the projected image of the compensation index on the light receiving means or the difference between when the image is calibrated, environmental fluctuations such as temperature changes will occur as well. It is possible to make accurate measurements in a compensated form.

[0044]

As described above, according to the first invention, a component of an optical system,
A highly accurate ophthalmologic measuring device can be achieved which does not require expensive costs for a fixing method, a temperature sensor, and the like, and can prevent an error in a measurement value from occurring due to a change in an optical system due to an environmental change such as a temperature change.

Further, according to the second aspect of the invention, it is possible to achieve a highly accurate ophthalmologic measuring device capable of preventing the occurrence of an error in the measured value due to the fluctuation of any optical member of the measuring optical system due to the environmental change.

Further, according to the third aspect of the present invention, a more highly accurate ophthalmologic measuring device can be achieved in which the influence of the fluctuation due to the temperature change of the compensation projection system itself is reduced.

Further, according to the fourth aspect of the invention, it is possible to achieve a highly accurate ophthalmologic measuring apparatus in which the decrease of the measuring light quantity due to the guiding of the compensating light beam to the measuring optical system is suppressed.

Further, according to the fifth aspect of the invention, a highly accurate ophthalmologic measuring device can be achieved which can guide the compensating light beam to the measuring optical system without using the difference in wavelength which causes the problem of chromatic aberration.

According to the sixth aspect of the invention, the result of light detection of the corneal reflection image and the light beam from the compensating projection system can be processed by the same arithmetic processing circuit or program, thereby facilitating the construction and achieving high precision. An ophthalmic measurement device is achieved.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a corneal shape measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a measurement index.

FIG. 3 is a diagram showing an example of a corneal reflection image of a measurement index by the cornea of the eye to be examined.

FIG. 4 is a structural explanatory view of a corneal shape measuring apparatus according to the first embodiment.

FIG. 5 is an explanatory diagram of a diaphragm.

FIG. 6 is an explanatory diagram of a compensation index.

FIG. 7 is a diagram illustrating an image of a compensation index on a light detection unit.

FIG. 8 is an explanatory diagram of a corneal reflection image during measurement and a corrected corneal reflection image.

FIG. 9 is an explanatory diagram of an image of a compensation index during measurement and an image of a compensation index during configuration.

FIG. 10 is a structural explanatory view of a corneal shape measuring apparatus according to a second embodiment of the present invention.

FIG. 11 is a diagram showing another example of a compensation index.

[Explanation of symbols]

2 indicators for measurement 4 Light splitting member 6 Light detection means 9 Control means 10 storage means 12 Compensation indicators 13 Illumination light source 14 Light splitting member

Claims (4)

(57) [Claims] 1. A measuring projection for projecting a measuring target onto an eye to be examined.
Projecting the shadow system and the reflected light of the measuring light flux from the subject's eye onto the light detection means
The optical characteristics of the eye to be examined are calculated based on the measurement optical system and the detection of the reflected light from the photodetector.
In the ophthalmologic measuring device having a calculating means for outputting, at least one of the measuring optical system including an optical path synthesizing member.
A compensating target with the same shape as the measuring target through the
Compensation projection system for projecting on the photodetector and reflection image formation for forming a reflection image from the measurement site of the eye to be examined
Position and a position substantially equivalent to the optical path combining member.
Stored compensation target and reference image data of the target
Storage means for storing the compensation light flux detection result by the photodetector , and the storage means.
By the calculation means using the image data stored in the stage
An ophthalmic measurement device characterized by compensating for eye characteristic measurement values
Place 2. Shapes of the measurement target and the compensation target
The eyes of claim 1, wherein both are substantially ring-shaped.
Measuring device. 3. The optical path combining means has wavelength selectivity.
The ophthalmic measurement device according to claim 1, wherein 4. The compensation projection system according to claim 1, further comprising a movable mirror that can be inserted into and removed from the measurement optical system for guiding the compensation light beam to the measurement optical system. Ophthalmic measuring device.