JPH024308A - Visual acuity inspection instrument - Google Patents

Abstract

PURPOSE:To easily test contact sensitivity with satisfactory accuracy by dividing the illumination optical system of a target, respectively controlling the light quantity of divided illumination light beams, illuminating the target from a back side with one of the illumination light beams and after that, causing the divided illumination light beams to be coincident again. CONSTITUTION:One of light beams to be outgoing from a lamp 1 is reflected by a mirror 2 and after that, passed through a lens 3. Then, the transmitting quantity of the light beam is limitted by a filter 14 of a filter disk 4 and the light beam illuminates a chart 16 of a chart disk 4 from the back side. The image of the chart 16 is passed through a half prism 6 and image-formed on a screen by an objective lens 7. Samely, the light beam to be outgoing from the lamp 1 is reflected by a mirror 8 and after that, passed through a lens 9. Then, the transmitting quantity is limited by a filter 13 of the disk 4 and the light beam is reflected by a mirror 10. After that, the light beam goes to be co-axial with the light beam, which illuminates the chart 16 with the half prism 6, and the light beam is projected through the objective lens 7 on a screen 11. At such a time, a filter is arranged on the disk 4 so that the sum of transmission factor for the filters 13 and 14 of the disk 4 can be constant. Then, when a motor 12 is revolved, only a contrast ratio can be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a visual acuity testing device, and more specifically to a device that can quantitatively test the contrast sensitivity of an eye to be examined.

[Prior Art] In most cases, the visual acuity measured by a general visual acuity test and the visual acuity in daily life match, but there are a small number of people who complain of a discrepancy between the two. Such people often have changes in the anterior segment of the eye or the medial opacity due to corneal opacity or cataracts.

The discrepancy between measured visual acuity and visual acuity in daily life can be explained as follows.

That is, a visual acuity test using a standard visual acuity chart merely tests visual acuity for small objects with high contrast ratios. For example, in cataract patients, opacity of the crystalline lens causes light scattering and reduces the contrast of the image at the fundus, but it does not affect the optical focal position of the image. Even if the text is vague, it may still be readable as text. In normal visual life, there are many conditions in which scattered light tends to increase, and because we often see objects that do not have high contrast, some patients with mild cataracts have difficulty in measuring visual acuity and visual acuity in daily life. will complain of discrepancies.

To detect such discrepancies, the following contrast sensitivity testing device was developed.

It has a 5-stage distance or near vision chart whose density changes like a sine wave so that it looks like blurry gray stripes, and each spatial frequency chart has a 9-stage chart whose contrast decreases in turn. It is made up of. The examinee is asked to indicate the chart that appears to have the lowest contrast in each row and its orientation, and the characteristics of the recorded results are used for screening for cataracts and glaucoma, evaluation of contact lenses, etc.

[Problems to be Solved by the Invention] However, the conventional device as described above has the disadvantage that a large number of visual targets must be prepared, resulting in an increase in size of the device.

Moreover, it is therefore difficult to incorporate it into an eye chart projector or an autorefractometer, and there is the disadvantage that it must be an independent device.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide a compact device that can easily test contrast sensitivity with high accuracy and that can be easily incorporated into other devices.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a means for dividing an illumination optical system for an optotype in a visual acuity testing apparatus that performs a visual acuity test by presenting an optotype to a subject. and a means for adjusting the light intensity of each of the divided illumination lights, and a means for aligning the divided illumination lights again after one of the divided illumination lights illuminates the optotype from the rear side. There is.

Furthermore, the means for adjusting the amount of illumination light according to the invention is characterized in that the means for adjusting the amount of illumination light is shared by the divided illumination optical systems by arranging filters in a fixed positional relationship in order to obtain a predetermined contrast ratio.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

! FIG. 1 is a schematic diagram of the arrangement of an optical system of an embodiment of the present invention relating to a projection type visual acuity tester.

Reference numeral 1 denotes a lamp for illuminating a chart (optical target).

In this embodiment, one lamp is used, but it is also possible to provide two lamps for each optical path.In this case, the light iI of the lamp itself can be reduced in consideration of aging deterioration of the lamp. Adjustment means will be required. 2, 8, and 10 are mirrors for changing the traveling direction of the illumination light beam.

3.9 is a condenser lens that converts the light beam emitted from the lamp 1 into a parallel light beam.

4 is a filter disk, the shape of which is shown in FIG.

The filter disk 4 has many filters arranged on the same circumference of the disk to determine the amount of transmitted light! has been done. Second
In the figure, eight filters are arranged, but by arranging more filters, a multi-step contrast test becomes possible.

In this embodiment, since the light intensity adjustment of the illumination system divided into two is realized by one filter disk, the transmittance of both filters 13 and 14, which are located symmetrically with respect to the center of the disk so that the background brightness is equal, is The sums of are equal.

12 is a filter disk motor for rotating the filter disk 4;

5 is a chart disk, and as shown in FIG. 3, optotypes for visual acuity testing including a chart (opotype) for general visual acuity testing are arranged on the same circumference of the disk. The number and types of charts (optotypes) on the drawings are merely for convenience of explanation and have no special meaning. Of course, a spatial frequency visual target as described in the prior art may also be used.

6 is a half mirror which combines the divided illumination light beams on the same axis again.

7 is the chart of Chard disk 5 (
The image of visual target) 16 is projected onto the screen 11.

Note that, of course, an optical element such as a beam splitter may be used to split the illumination light beam.

The operation of the embodiment configured as described above will now be explained based on the block diagram shown in FIG.

When the switch on the operation panel 20 is operated, the lamp 1 lights up. One of the luminous fluxes emitted from the lamp 1 is reflected by the mirror 2 and becomes a parallel luminous flux by the condenser lens 3, and the amount of transmission thereof is limited by the filter 14 of the filter disk 4.

The light beam transmitted through the filter 14 illuminates the chart 16 on the chart disk 5 from behind. The image of the chart 16 passes through the half prism 6 and is focused on the screen by the objective lens 7 as shown in FIG.

Similarly, the light beam emitted from the lamp 1 is reflected by the mirror 8, becomes a parallel light beam by the condenser lens 9, and the amount of light transmitted is limited by the filter 13 of the filter disk 4.

The light beam transmitted through the filter 13 is reflected by the mirror 10, becomes coaxial with the light beam illuminating the chart 16 at the half prism 6, and is projected onto the screen 11 via the objective lens 7.

Next, a chart projection image (
The brightness and contrast of FIG. 4) will be explained.

The brightness of the characters 17 in the projected image of the chart is determined by the amount of illumination light that passes through the filter 13, and the brightness of the background 18 is determined by adding the amount of illumination light from the optical system that passes through the chart 16 to the former.

Now, the transmittance of the filters 13 and 14 on the filter disk are A% and B%, the amount of illumination light after passing through each filter is la, lb, and the brightness on the screen due to each illumination light is Ia. , Ib, then IaO(La Lac>ζA I bocLb Lbc-CB The contrast ratio C of the character in the projected image of the chart is the character 1
Letting the brightness of 7 be It and the brightness of the background as Ig, it is given by the following equation.

IQ and It are given by the following formula.

■Ω=1a+1b I I=Ia Therefore, since the contrast ratio of the chart image is determined by the transmittance of the filter of the filter disk 4, A and B
By placing a filter such that the sum of the values is constant on a filter disk and rotating the filter disk motor 12, it is possible to change only the contrast ratio without changing the background brightness of the chart.

Therefore, when changing the contrast ratio, use the operation panel 2.
0 switch, the microcomputer 21. Filter disk motor 1 via motor drive circuit 22
2 and place the predetermined filter.

To change the chart, change the motor drive circuit 2 in the same way.
3, the chart disk motor 15 is rotated to display a predetermined chart.

The test subject's response results obtained through such operations are input to the microcomputer 21 and are sent to the display drive circuit 24.
The signal is outputted to the display unit 25 via the printer drive circuit 26 and by the printer 27 via the printer drive circuit 26.

Fig. 6 is a schematic diagram of the arrangement of an optical system of an embodiment incorporated into an autorefractor for both subjective and objective sensing.

Autorefractors that can be used for both subjective and objective senses are well known, so
I will limit myself to explaining simple operations.

The light from the illumination lamp 1 illuminates the optotype in the chart disk 5 from behind in the same manner as in Example 1, passes through the second relay lens 48, etc., is reflected by the mirrors 38, 3.5, and then illuminates the subject's eye. It is projected onto the fundus of the eye and the subject's eye is forced to fixate.

The measurement light flux emitted from the light source 30 passes through condenser lenses 31 and 32, a spot diaphragm 33, and an objective lens 34, and reaches the fundus of the eye 36 to be examined.

The reflected light flux from the fundus is reflected by the mirror 35, passes through the objective lens 37, is reflected by the mirror 39, and then passes through the relay lens 4.
0,42, and is projected onto the light receiving element 45 via a band-shaped corneal reflection removal mask 41, a moving lens 43, and a relay lens 44, which are arranged at a position conjugate with the cornea. The projected image incident on the light receiving element is supplied to the microcomputer as a digital signal.

When the measurement button is pressed after completing the alignment for the eye to be examined, the microcomputer moves the spot diaphragm 33 and the moving lens 43 until the spot diaphragm 33 is at a position conjugate with the fundus of the eye 36 to be examined. At the same time, an optotype for frost and snow is imaged on the fundus of the eye to be examined, and then the first relay lens 46 is moved so that a cloud is applied by an appropriate diopter.

After that, the measurement light source 30. The condenser lens 31, the corneal reflection removal mask 41, and the light receiving element 45 are arranged 180 degrees around the optical axis.
Move 0 times. During rotation, the spot diaphragm and the movable lens move in response to signals from the light receiving element, and depending on the amount of movement, the refractive power for each meridian can be obtained, and the refractive power of the entire eye to be examined can be obtained.

After the objective measurements described above are completed, when the subjective measurement switch is pressed, the chart disc motor rotates under the control of the microcomputer, the chart disc rotates, and the general optotype for the visual acuity test is presented. At the same time, the first relay lens 46 and the Stokes type cylindrical lens 47 rotate, and the eye to be examined can see the general optotype for visual acuity test with the refractive power obtained by objective measurement corrected.

If the visual acuity is not sufficient at this stage, subjective measurement is further performed by operating the first relay lens 46 and the Stokes cylindrical lens 47 while changing the visual target.

With sufficient visual acuity obtained, a contrast test is performed in the same manner as in Example 1 to confirm whether there are any abnormalities.

In addition, when the moving optical system of the visual target system and the measuring system are shared or linked, as in the patent application No. 62-235829 filed by the present applicant entitled "Eye refractive power measuring device", the cloud visual target is used as the visual target of another visual target. It must be placed separately from the beacon and offset by an amount equivalent to the amount of fog.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, contrast sensitivity can be easily tested with high accuracy, and since it is compact, it can be used in other devices such as autorefractometers and projection-type visual acuity measuring machines. Can be easily incorporated.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the arrangement of an optical system according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a filter disk, FIG. 3 is a diagram showing an example of a chart disk, and FIG. 4 is a diagram showing an example of a chart disk. FIG. 5 is a block diagram of the apparatus shown in FIG. 1, and FIG. 6 is a schematic diagram of the arrangement of the optical system of the apparatus incorporated into an autorefractometer for both subjective and objective functions. 1... Optotype light source 4... Filter disk 5... Chart disk 6... Half prism 11... Screen

Claims (1)

[Scope of Claims] 1) A visual acuity testing device that performs a visual acuity test by presenting an optotype to a subject, comprising: means for dividing the illumination optical system of the optotype, and adjusting the light intensity of the divided illumination light, respectively. A visual acuity testing device comprising: means for illuminating an optotype from behind with one of the divided illumination lights and then making it coincide again with the other illumination light. 2) A visual acuity testing device characterized in that the means for adjusting the amount of illumination light as described in item 1 is a disk plate on which a plurality of filters are arranged. 3) The means for adjusting the amount of illumination light described in item 1 is common to the divided illumination optical system, and the filters are arranged in a constant positional relationship to obtain a predetermined contrast ratio. Vision testing device. 4) A visual acuity testing device, characterized in that the visual acuity testing device according to item 1 or 3 is incorporated into an optotype system of an automatic eye refractometer.