JPS61185247A - Ophthalmic measuring apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ophthalmological measuring device capable of detecting whether the light amount loss of an optical system is within a normal operating range.

[Prior art] For example, a non-contact tonometer that uses air pulses blows air pulses onto the cornea from the axial direction of the device, and measures intraocular pressure based on the time it takes for the cornea to applanate. However, if the corneal apex and the horizontal ocular axis do not exactly match the axis of the device, accurate intraocular pressure cannot be measured. In a non-contact tonometer, a positioning optical system is provided to align the corneal vertex with the axis. Then, the examiner determines the moment when the corneal apex of the examinee coincides with the axis using this positioning means, turns on the air pulse circuit, and emits an air pulse.

In the conventional device shown in FIG. 4, l is an illumination lamp, and light from this illumination lamp l is transmitted to a positioning optotype 2 drawn on a diffuser plate, and to a guichroic mirror that transmits infrared and reflects visible light. 3. Via the total reflection mirror 4 and the lens 5, it is reflected by the half mirror 6 to the left, and is directed to the corneal curvature center Eb of the eye E through the objective lens 7, which has an air pulse emitting orifice 7a at the center. It is designed to focus light. Further, reference numeral 8 denotes an infrared light emitting diode arranged behind the guichroic mirror 4 and provided at a position conjugate with the optotype 2.

The optotype image directed toward the center of corneal curvature Eb is reflected on the surface of the cornea Ec, becomes parallel light by the objective lens 7, and passes through the half mirror 6 and lens 9 to the gicroic mirror 10 that reflects infrared light and transmits visible light. , and the image is formed on a transparent plate 11 on which a sighting mortar is drawn. Note that the infrared light is reflected by the guichroic mirror 10. An image is formed on an infrared detection diode 12 located at a conjugate position with the transparent plate 11. The examiner can match the position and focus of the visible light target image on the aiming circle through the eyepiece 13 while moving the entire apparatus. 14 is an infrared light emitting diode that emits parallel light and projects external light obliquely onto the cornea Ec. When the vertex of the cornea Ec is applanated from a convex surface to a flat surface by an air pulse, the The arrangement is such that the emitted light is most efficiently focused onto the infrared light emitting diode 16 via the lens 15.

When the examiner presses the measurement button when the alignment is completed, an air pulse having a known pressure-time relationship is emitted through the orifice 7a of the objective lens 7 toward the vertex of the cornea Ec. The intraocular pressure can be determined by measuring the time it takes for the apex of the cornea Ec to change from a convex surface to a flat surface using the output of the infrared light emitting diode 19. When the measurement button is pressed, if the image of the alignment optotype 2 is not correctly within the aiming circle of the transparent plate 11, an infrared detection diode 12 is installed at a conjugate position with the transparent plate 14 so that an air pulse is not emitted. The measurement button is configured to work only when an output of . However, if the optical system of the apparatus becomes dirty with dust, fingerprints, etc., the attenuation of the optotype light increases even if the alignment is performed accurately. Therefore, the initially set air pulse emission signal strength cannot be obtained, which is equivalent to misalignment, and the air pulse will not be emitted even if the measurement button is pressed, and the optical system may be slightly dirty. At this stage, there is a drawback that the air pulse is in an unstable state where the air pulse may or may not be emitted depending on the difference in the reflectance of the cornea Ec.

[Object of the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples, to be able to predict the time to clean the optical system before measuring the eye to be examined, and to improve the accuracy of the alignment light-emitting element and light-receiving element. An object of the present invention is to provide an ophthalmologic measuring device that can detect a decrease in light intensity due to deterioration.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to provide a measurement apparatus having means for projecting an optotype onto a subject's eye through an objective lens and receiving the reflected image through the objective lens. Ophthalmological measurement characterized by comprising: a reflecting member which is removably placed in front of a lens and has a constant reflectance, and a calculation means for comparing and calculating a received light output level due to light reflected from the reflecting member with a predetermined level. It is a device.

[Embodiments of the Invention] The present invention will be described in detail based on embodiments illustrated in FIGS. 1 to 3.

FIG. 1 shows an embodiment of the present invention, in which an objective lens 7 is held in a lens barrel 20 placed on the eye E side of the optical system in FIG. is covered with a removable objective lens cap 21,
A reflecting plate 22 is attached to the surface facing the objective lens 7. The lens cap 21 is butted against a step provided on the lens barrel 20 so that the distance between the objective lens 7 and the reflecting plate 22 is a predetermined distance, and the presence of the lens cap 21 is detected by a microswitch 23. It has become so.

FIG. 2 shows the output side of the infrared detection diode 12 shown in FIG. This is the output when the image is accurately formed on the top, and T2
The output of the infrared detection diode 12 has decreased due to dirt in the optical system, and it is close to the output level v2 at which it should be determined that the alignment is misaligned.If the output decreases below this level, the image may not be accurately formed. It also does not fire air pulses. T3
is a lens cap 21 having a reflector 22 according to the present invention.
This is the output when the lens cap 21 is attached, and is lower than the output level v3 for emitting air pulses, so there is no risk of air pulses being emitted with the lens cap 21 attached.
4 indicates the output level when the lens cap 21 is attached while the optical system remains dirty, and the amount of attenuation from V1 to v2 is equal to the amount of attenuation from V3 to v4.

Therefore, if you cover the lens cap 21 and make sure that the output of the infrared detection diode 12 due to the reflected light from the reflector plate 22 is not below the level of v4, you can measure the eye E and align it accurately. Despite this, it is possible to prevent the phenomenon in which the output level of the infrared detection diode 12 becomes lower than v2 due to dirt in the optical system and air pulses are not emitted. In addition to dirt on the optical system, the output level of the infrared detection diode 12 may also decrease due to a decrease in the amount of light due to deterioration of the infrared detection diode 12, but this can be detected in the same way.

FIG. 3 shows a block circuit configuration diagram for stopping the comparison calculation/warning display φ measurement system. Infrared detection diode 12
The output obtained is amplified by the amplifier 24 and becomes the single power of the comparator 25. A reference voltage preset by fixed or variable resistors 26 and 27 is input to the other input terminal of the comparator 25, and the two are compared in the comparator 25. Further, an analog switch 28 is inserted on this reference voltage side, and a microswitch 23 that detects that the lens cap 21 is attached to the lens barrel 20 sends on/off information of the switch 23 to a comparator 25. It is designed to give.

For example, if the signal from the infrared detection diode 12 is input to the positive input of the comparator 25, and the reference voltage is input to the negative input,
The output of the comparator 25 has a threshold level, which is positive if the reflected light is larger than the reference voltage, and 0 if it is smaller.
Binarized information appears like this. 29 and 30 are a warning display element and a measurement stop circuit, respectively, and comparator 2
When the output of 5 is O, the warning display element 29 warns the examiner that the objective lens 7 is dirty. This warning display element 29
Possible sources include light-emitting elements such as LEDs and sounds such as buzzers.

Also, even if the examiner does not notice this warning.

If the measurement button is pressed as it is, the measurement stop circuit 30 prevents the air pulse from being emitted to the subject. Thus, use of this warning system may result in double warnings being given to the examiner. Further, 31 is a switch that cancels this warning system when returning to normal measurement after the examiner recognizes the warning and sufficiently cleans the objective lens 7; this switch 31 does not cancel the warning system. In this case, normal measurement cannot be performed even if the microswitch 23 is turned off.

[Effects of the Invention] As explained above, the ophthalmological measurement device according to the present invention detects dirt on the device optical system by measuring the reflector provided on the lens cap, and can know when to clean the device optical system. At the same time, it is also possible to detect a decrease in the amount of light due to deterioration of the light emitting element or light receiving element.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a lens cap with a reflector showing an embodiment of the ophthalmological measuring device according to the present invention, Figure 2 is a characteristic diagram of the output level of an infrared detection diode, and Figure 3 is a block diagram of a warning system. The configuration diagram, FIG. 4, is a configuration diagram of a non-contact tonometer. 1 is an illumination light source, 2 is an optotype plate, 8.14 is an infrared light emitting diode, 3 and 1O are dichroic mirrors, 6 is a half mirror, 17 is an objective lens, 7a is an orifice, 11
13 is a transparent plate, 13 is an eyepiece, 12.16 is an infrared detection diode, 20 is a lens barrel, 21 is a lens cap, 22 is a reflector, and 23 is a microswitch. Patent applicant Canon Co., Ltd. 1WA 12 prisoners

Claims (1)

[Scope of Claims] 1. In a measuring device having means for projecting an optotype onto the subject's eye through an objective lens and receiving the reflected image through the objective lens, the measuring device is provided with a means for projecting an optotype onto the eye to be examined through an objective lens, and a means for projecting a visual target onto the eye to be examined through the objective lens, wherein a constant reflection 1. An ophthalmological measuring device comprising: a reflecting member having a constant ratio; and a calculation means for comparing and calculating a received light output level of light reflected from the reflecting member with a predetermined level. 2. The ophthalmological measuring device according to claim 1, further comprising warning means for issuing a warning when the result of the comparison calculation by the calculation means deviates from a set value. 3. The ophthalmological measuring device according to claim 2, further comprising means for issuing a warning by the warning means and for stopping the operation of the measuring system. 4. The ophthalmological measuring device according to claim 1, wherein the reflecting member is installed at a fixed position in front of the objective lens. 5. Means for detecting that the reflecting member is installed in a fixed position; and Claim 4, wherein the calculating means is activated only when the reflecting member is installed in a fixed position.
The ophthalmological measuring device described in Section. 6. The ophthalmological measuring device according to claim 1, wherein the reflective member is provided on the inner surface of the protective cover of the objective lens.