JPH0994222A - Apparatus for examining visual acuity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the presentation of an accurate target even on a near distance examination by providing a target plate having a plurality of examination targets thereon, lighting the target plate from the backside and regulating a means for adjusting the transmittance according to a signal from a selecting means. SOLUTION: Putting on an electric switch, a regulating circuit actuates a back light 24 of a target presenting unit to light, to turn on all of liquid crystal devices 23a of a liquid crystal panel 23 to cut off so as not to transmit the back light. As a result, the presenting face of the target is looked as a deep-black state because the transmitted light is screened by a region (the surrounding region 22d) where the liquid crystal device 23a is not formed on the liquid crystal panel 23 and is printed black. At this state, by operating a target selection switch to cut off the electricity for the liquid crystal device 23a at the position corresponding to a selected target, and thereby transmitting the lighting light at this position to present only the examination target, the visual acuity of the subject can be determined according to the response of the subject.

Description

Detailed Description of the Invention

[0001]

[0001]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual acuity test apparatus for presenting a test visual target on an eye to be examined for visual acuity test, and more particularly to a visual acuity test apparatus suitable for presenting one-character visual target.

[0003]

[0002]

[0004]

2. Description of the Related Art Conventionally, as a visual acuity test device for presenting a single-character optotype, test optotypes printed on a semi-transparent plate are individually illuminated from the back of the optotype by a lighting device such as a lamp.
A back-illuminated type that specifies an optotype to be read by the subject and a liquid crystal display type that presents one test optotype such as a Landolt ring formed by a liquid crystal member are known.

[0005]

[0003]

[0006]

However, the former back-illuminated device has the following drawbacks. That is, in order to specify each optotype, a light source corresponding to each optotype must be provided, which increases the number of light sources, which is economically disadvantageous.

Further, the structure of the wiring of the light source becomes complicated,
Since the device itself is large, it is difficult to install and move.

Further, since the light source is individually arranged for each inspection target, the brightness of the light source is likely to differ depending on the frequency of use. For this reason, the optotype presenting conditions may be different, and the inspection result may be inaccurate.

Furthermore, in the case where the test target is printed on the semi-transparent plate, the target other than the specified target can be seen by the subject, so that the subject can easily remember the target. , It is difficult to get accurate test results.

[0010]

The latter liquid crystal display type device has the following drawbacks. The inspection target formed of liquid crystal becomes less precise as the size of the target decreases. In particular, in a short-distance simple type device, an inspection target having a high visual acuity value is considerably small, which makes it difficult to manufacture.

Further, when the inspection target is displayed on a portion having a wide target display surface, if the size of the target is small, there is a problem that the subject cannot immediately judge the displayed position. is there.

[0012]

In view of the above-mentioned drawbacks, the present invention provides a visual acuity test apparatus having a simple structure capable of presenting a single-character optotype with high accuracy even in a short-distance examination and easily specifying the presenting location. Providing is a technical issue.

[0013]

[0006]

[0014]

In order to achieve the above-mentioned object, the visual acuity test apparatus of the present invention is characterized by having the following configuration. (1) In a visual acuity test apparatus for presenting a test target for testing the visual acuity of an eye to be examined, a target plate on which a plurality of test targets are formed, and a target for giving a predetermined contrast to the test target. Background region forming means for forming a background region divided into a plurality of background regions of the target for distinguishing the presenting target and the non-presenting target, and electro-optically changing the transmittance of the background region. Transmittance variable means, back illumination means for illuminating the optotype plate from the back side, selection means for selecting an optotype to be presented from among the examination optotypes, and the transmission based on a signal from the selection means. Control means for controlling the rate varying means.

[0015]

(2) The test target of (1) is characterized by being printed on a target plate.

[0016]

(3) The transmittance varying means in (1) is a liquid crystal.

[0017]

(4) In the visual acuity testing device of (1),
The background area is formed of a liquid crystal element, and a peripheral area surrounding the background area is printed in black.

[0018]

(5) The visual acuity test apparatus of (1) includes optical element arranging means for switching and arranging necessary optical elements in front of the eye to be inspected, and the optotype plate is arranged at a predetermined short distance. It is characterized in that the optical distance to the inspection target is switched to a predetermined distance by the optical element by the arranging means.

[0019]

[0011]

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an external configuration diagram of the apparatus of the embodiment.
The device of the embodiment is a simple visual acuity test device for inspecting the influence of the visual function of VDT work.

Reference numeral 1 is a base, and 2 is an optotype presenting section (details will be described later). The optotype presenting part 2 is held by a support column 3 fixed to the base 1, and its optotype presenting surface is installed at a distance of 50 ◆ with respect to the eye to be examined fixed to the chin rest unit 4. .

The chin rest unit 4 has a chin rest support base 5 fixed to the base 1, a chin rest 6 movable up and down with respect to the chin rest support base 5, and a chin rest support base 2 suspended from the chin rest support base 5. It is composed of a pillar 7 of a book, an erection member 8 erected on the upper end of the pillar 7, and the like.

An optical unit 10 for switching and arranging necessary optical elements in front of the eye to be inspected is suspended from the erection member 8 via a mounting member. The optical unit 10 includes a lens for 5 m, an aperture, a shield plate, etc. arranged on the same circumference to optically set an inspection target for an inspection distance of 50 cm of the target presenting section 2 described later to an inspection distance of 5 m. A pair of discs 11, a pulse motor 12 for rotating the left and right discs 11, a disc 11 and a pulse motor 12 respectively.
It is configured by two left and right suspension plates 13 that suspend and support the two, a distance adjustment unit 14 that adjusts the interval between the two left and right suspension plates 13, and the like.

[0024]

Reference numeral 16 denotes a remote controller connected to the apparatus main body by a cable, which is a switch for selecting an optotype to be presented on the optotype presenting section 2 and an optical unit arranged in front of the eye to be examined of the optical unit 10. Changeover switch to change the system,
It has various switches such as a start switch for starting measurement when performing automatic measurement and a group of direction input switches for inputting the direction answered by the subject during automatic measurement.

Reference numeral 17 is a printer, and 18 is an IC card writer for writing the measurement results in an IC card.

[0026]

Next, the structure of the optotype presenting section 2 will be described with reference to FIG. Reference numeral 20 is an outer frame of the optotype presenting section 2, and reference numeral 21 is a transparent glass plate provided with an antireflection film. Reference numeral 22 is an optotype plate made of a semitransparent film, and a radial astigmatism inspection target 22a and 24 Landolt ring targets 22b for the inspection distance 50 ◆ are formed on the surface by printing or the like. Landolt ring targets 22b having visual acuity values of 0.1 to 1.2 are prepared, and three of them having the same visual acuity values are provided in different cut directions. Each target 22a,
A circular background area 22c is formed around 22b to give a predetermined contrast to the visual target.
A peripheral region 22 in which black is printed almost uniformly around c
d is formed.

By using a printing technique, the test target such as the Landolt ring can be processed with sufficient precision as a target plate even for a target having a small size or a fine portion of the target. .

[0028]

Reference numeral 23 is a liquid crystal plate for selectively illuminating the visual target. The liquid crystal plate 23 includes the background regions 22 of the optotype plate 21.
At each position corresponding to c, a liquid crystal element portion 23a having a region slightly larger than the background region 22c is provided. This liquid crystal element portion 23a
Does not transmit light when an AC voltage is applied, and conversely transmits light when the energization of voltage is cut. 24 is an optotype plate 22
The back light 24 is a back light for illuminating the back surface of the optotype plate 22.

[0029]

In the device having the above structure,
The operation will be described with reference to the block diagram of the main control system of FIG.

When a power switch (not shown) is turned on, the control circuit 30 of the apparatus, via the backlight drive circuit 31,
The backlight 24 of the optotype presenting unit 2 is turned on. In addition, the control circuit 30 drives the liquid crystal plate drive circuit 32 at the time of starting the device to energize all the liquid crystal element portions 23a of the liquid crystal plate 23 to bring the backlight illumination light into a cutoff state.
When the liquid crystal element portion 23a is energized, the liquid crystal element portion 23a does not transmit the back illumination light of the backlight 24 to the optotype plate 22 side. Further, the region on the liquid crystal plate 23 where the liquid crystal element 23a is not provided transmits the back illumination light of the backlight 24, but the transmitted light is blocked by the black printing of the peripheral region 22d of the optotype plate 22. Therefore, when a voltage is applied to all the liquid crystal element parts 23a, the optotype presenting surface of the optotype presenting part 2 looks black.

[0031]

Next, the examinee's eye is placed on the chin rest unit 4 (the height of the chin rest 6 and the left and right distances of the disc 11 are adjusted if necessary). The eye to be inspected is an inspection disk 11
The optotype presenting surface of the optotype presenting unit 2 can be seen through the opening, the lens, or the like.

When the preparation of the examinee is completed, the examiner operates the switch of the controller 16 to switch and select the optical element arranged in front of the examinee's eye. For example, a 5 m distance test of the right eye is performed. The control circuit 30 receives the switch signal from the controller 16 and drives the left and right pulse motors 12R and 12L via the drive circuits 33 and 34 to rotate the left and right disc boards 11 respectively, so that the subject is examined. A shielding plate is placed in front of the left eye and a 5 m lens is placed in front of the right eye.

[0033]

Next, the optotype selection switch of the controller 16 is operated to select the optotype to be presented on the optotype presenting section 2.
The target is selected by pressing the switch corresponding to the direction of the Landolt's ring for each visual acuity value display. When the target selection signal is input from the controller 16, the control circuit 30 drives the liquid crystal plate drive circuit 32 to cut off the power supply to the liquid crystal element 23a at the position corresponding to the selected target. The illumination light of that part is transmitted. The transmitted illumination light illuminates the background area 22c of the specific target, and as shown in FIG. 3, the illumination light is placed in the center of the white portion (the background area 22c corresponding to the liquid crystal element portion 23a where the electrification is selectively cut). Only certain test targets are presented. In this way, the background region 22c corresponding to the selected optotype appears in the background of the black optotype presenting surface, and the optotype is specified. Therefore, even a small optotype with a high visual acuity value can be detected. The person can immediately determine the presentation position.

The examiner operates the switches of the controller 16 to sequentially switch and present the examination targets to proceed the examination, and judge the visual acuity based on the response of the examinee.

[0035]

Further, the apparatus of the embodiment is capable of a 50 cm visual acuity test, and in this case, the disc 1 is placed in front of the eye to be inspected.
The opening provided in 1 is arranged. The subject can see the optotype of the optotype presenting unit 2 at the examination distance of 50 cm through the opening, and the examiner similarly switches the presenting optotype by the switch operation of the controller 16 to perform the examination.

Further, the control circuit 30 of this embodiment has a program for automatic measurement, and the controller 16
The control circuit 30 starts the program by the input of the start switch. Optical unit 1 in front of eye
A predetermined optical system of 0 is arranged, and the liquid crystal plate 23 is provided so that the optotype presenting section 2 presents the optotype of the preset visual acuity value.
Is controlled and the inspection is started. The examiner inputs the response of the subject through the input switch group. The control circuit 30 determines whether the response is correct or not based on the signal, sequentially switches the optotype presenting according to a program stored in advance based on the determination result of whether the response is correct, and automatically determines the visual acuity value of the eye to be inspected.

[0037]

In the above embodiment, the black printing of the peripheral area 22d for blocking the backlight illumination light is performed on the optotype plate 22. However, of course, it may be performed on the transparent glass plate 21 or the liquid crystal plate 24 side. good.

The specific presentation of the optotype by the backlight illumination light transmitting region and the blocking region is performed in the peripheral region 22 as in the embodiment.
d is uniformly printed in black, and only the background area of each inspection target is composed of liquid crystal elements, and the entire liquid crystal plate 23 is composed of liquid crystal, and a portion corresponding to the background area 22c of the selected inspection target is formed. You may control so that it may permeate | transmit.

Further, as the liquid crystal plate 23, those utilizing various electro-optical effects can be used, and a display such as a CRT can be used instead of the liquid crystal plate 23 and the backlight 24.

Although the present invention has been described above based on an example in which it is applied to a simple optotype inspection apparatus, the present invention is not limited to this and can be used in various visual acuity inspection apparatuses.

[0041]

[0020]

[0042]

As described above, according to the present invention, it is possible to present a character-by-character optotype with high accuracy with a relatively simple structure.

Further, even when presenting a small optotype having a high visual acuity value, the subject can easily and immediately determine the presentation place.

[Brief description of drawings]

FIG. 1 is an external configuration diagram of a visual acuity test apparatus according to an embodiment.

FIG. 2 is an internal configuration diagram of an optotype presenting unit of the visual acuity test apparatus according to the embodiment.

FIG. 3 is a presentation example of an optotype presenting unit of the visual acuity test apparatus according to the embodiment.

FIG. 4 is a control diagram of the visual acuity test apparatus according to the embodiment.

[Explanation of symbols]

 2 optotype presenting part 22 optotype plate 22b Landolt ring optotype 22c background region 22d peripheral region 23 liquid crystal plate 23a liquid crystal element part 24 backlight 30 control circuit 31 backlight drive circuit 32 liquid crystal plate drive circuit 32

Claims (5)

[Claims] 1. A visual acuity test apparatus for presenting a test target for testing the visual acuity of an eye to be examined, and a target plate on which a plurality of test targets are formed, and a predetermined contrast is given to the test target. Background region forming means for forming a background region that is divided into a plurality of background regions for distinguishing the presenting target and the non-presenting target, and the transmittance of the background region electro-optically. Transmittance varying means for changing, back illumination means for illuminating the optotype plate from the back side, selection means for selecting an optotype to be presented from among the examination optotypes, and based on a signal from the selection means And a control unit that controls the transmittance varying unit. 2. The visual acuity test apparatus according to claim 1, wherein the test optotype of claim 1 is printed on an optotype plate. 3. The visual acuity test apparatus according to claim 1, wherein the transmittance varying means is liquid crystal. 4. The visual acuity test apparatus according to claim 1, wherein the background area is formed of a liquid crystal element, and a peripheral area surrounding the background area is printed in black. 5. The visual acuity test apparatus according to claim 1, further comprising an optical element arranging means for switching and arranging necessary optical elements in front of the eye to be inspected, wherein the optotype plate is arranged at a predetermined short distance, and the optical element arrangement is arranged. A visual acuity test apparatus characterized in that the optical distance to the test target is switched to a predetermined distance by an optical element by means.