JP3031425B2 - Moving object detection contrast threshold inspection 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 inspection apparatus for inspecting the visual function of an eye.

[0002]

2. Description of the Related Art As a method of examining eye diseases such as glaucoma that causes visual field impairment, a visual field test has been conventionally performed. In this visual field inspection, the eye to be inspected is positioned near the spherical center including the spherical center of the hemispherical projection screen, and the visual field measurement is performed while changing the target presenting position of the target projected on the projection screen. Is what you do. This method is also useful as a visual field test, but in the case of glaucoma, it has been reported that half of the optic nerve cells have already been lost when this test indicates that visual field damage has occurred. Previously, it was desired to detect a subjective abnormality and use it for screening. It has also been desired to detect abnormalities in diabetic retinopathy and the like at an early stage and utilize them for screening. Based on such a request, the present applicant has filed Japanese Patent Application No. Hei.
No. 114450 proposed a moving object detection threshold value inspection apparatus.

[0003]

In this examination, the test subject must be presented with a target having an accurately controlled contrast value. However, in the above-described apparatus, the influence of the brightness of the examination environment and the deterioration of the light source are considered. Inevitably, there is a problem that it is difficult to always present an optotype having an accurate contrast value to a subject.

[0004] The present invention was devised based on the above-mentioned demands, and always presents an optotype having an accurate contrast value to a subject to prevent visual impairment due to the onset of glaucoma and diabetic retinopathy. It is an object of the present invention to provide a device that can detect an abnormality at an early stage.

[Means for Solving the Problems] To solve the above problems, a moving object detection contrast threshold value inspection apparatus of the present invention has the following configuration. (1) a fringe target projection optical system for projecting a fringe target on a projection screen;
A contrast switching means for switching the contrast of the fringe target, a drive unit for oscillating the fringe target, an illumination optical system for illuminating the projection screen almost uniformly, and a light source disposed near the projection screen. A light detector for detecting the amount of light,
And an adjusting means for adjusting the light amount of at least one light source of the illumination optical system and the fringe target optical system based on the output from the photodetector.

(2) The contrast switching means of (1) is a switchable filter arranged in the fringe target projection optical system or a switch means for adjusting the light amount of the projection light source of the stripe target. Features.

(3) The photodetector of (1) is a projection screen.
It is characterized in that it is arranged almost at the center of the fringe target projected on the screen and used as a fixation target.

(4) The photodetector for detecting the light quantity of (1) has a light receiving window smaller than each width of the bright portion and the dark portion of the projected fringe target, and moves the fringe target by fringe viewing. It is characterized in that each light amount when a bright portion and a dark portion of the target cover the light receiving window is detected, and the light amount of the light source is adjusted based on the detected light amount.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to a specific description of an embodiment, an inspection principle based on the present inspection apparatus will be described. Examination of the visual function of the eye shows that there is a vertical connection composed of photoreceptors, bipolar cells, and ganglion cells, and a horizontal connection composed of horizontal cells and amacrine cells. The vertical connection converts light that has reached the photoreceptor cells into an electrical signal and transmits image information to the brain via the optic nerve. On the other hand, the horizontal connection is composed of horizontal cells located between visual cells and bipolar cells, and amacrine cells located between bipolar cells and ganglion cells, and is responsible for contrast enhancement, moving object detection, stereoscopic perception, etc. . It is said that this lateral connection allows a person to accurately see an object under a wide range of illumination from 1 to 10 ¹¹ , and to detect even a slight stain or dirt on a white wall.

By the way, in diabetic retinopathy, it is known that rhythm-like ripples related to lateral function abnormally become abnormal very early, and impairment of lateral function occurs early in visual field disorder. Paying attention to the fact that this is estimated, the present apparatus is to detect a subjective visual function abnormality that can correspond to the abnormality of the lateral function. In particular,
The stripes are imaged on the retina at an appropriate interval (the area where one horizontal cell has a connection, that is, about 200 μm is optimal on the retina), and the stripes are shaken and stimulated. The amplitude of this vibration may be equal to or more than の of the width of the stripe, and the frequency of the vibration is within a range that does not affect the static detection capability. If it is easy to set), it is easy to detect. It is examined how low contrast the subject can recognize the movement (fluctuation) of the stripe pattern projected on the center of the adaptation field at a low contrast. If the horizontal cells and the amacrine cells are functioning normally, it can be recognized even at a low contrast below a certain threshold set at the boundary between the normal person and the abnormal person. However, if these do not function properly, a low-contrast striped pattern cannot be recognized.

According to the present invention based on the above-described measurement principle,
The details of the embodiment will be described with reference to the drawings.Constitution  FIG. 1 is a light showing the configuration of the optical system of the inspection apparatus of the present embodiment.
It is a system layout plan. 1 is a light source of a target projection optical system.
Light from the halogen lamp 1
The light enters the disk 4 via the denser lens 2 and the aperture 3.
Stepless on the projection optical path on the disk 4 having a disk shape
Wedge type filter that changes transmittance
The disk 4 is rotated by the pulse motor 5.
Change the transmittance. In this embodiment, the transmittance is gradually increased.
The contrast of the fringe target ranges from 0.1% to 10%.
It is designed so as to have a resolution of 200 steps.

The light transmitted through the disk 4 illuminates the striped target plate 7 almost uniformly through the projection lens 6. A stripe pattern having a transmittance of 80% or more in a bright part and a transmittance of 0% in a dark part is drawn on the stripe target plate 7. The stripe target plate 7 is configured such that the stripe target (see FIG. 2) projected on the screen 13 has a viewing angle of 5 degrees and a stripe pitch of 0.5 degree of the eye to be examined. The fringe target plate 7 is vibrated by the fringe target driving unit 8 in a direction orthogonal to the fringe direction. The frequency of this vibration is 4 Hz and the amplitude is 0.2
5 degrees. The stripe optotype driving unit 8 in the present embodiment employs the following simple mechanism in consideration of the sufficiently small amplitude of the vibration. That is, by vibrating a vibration axis, one end of which is fixed to the stripe target plate 7 and the other end of which is fixed to the axis of the pulse motor, by forward and reverse rotation of the pulse motor, the stripe target plate 7 is rotated.
Vibrates.

The projection lens 10 includes a stop 9 and a mirror-1.
An image of the striped optotype plate 7 is formed at the center of the screen 13 via 1 and 12. The screen 13 has a hemispherical shape, a screen size of 20 degrees, and a gaze distance from the eye to be examined of 300 mm. The front of the screen 13 is covered in order to block the light on the outer periphery, and the subject can look through the central opening through the stripe target projected on the screen 13 with the left or right eye. ing.

Numeral 14 denotes halogen lamps, two of which are arranged on the left and right sides of the opening to illuminate the screen 13 uniformly. The background luminance of this screen is 500 cd / m ² , the background luminance is the brightness of the dark part of the stripe optotype, and the maximum value of the brightness of the bright part of the stripe optotype is about 10% brighter than the dark area by the disk 4. It is designed to be.

Reference numeral 15 denotes a light receiving element. The light receiving element 15 detects a change in luminance due to the influence of disturbance light or deterioration of the light source,
This is for maintaining the contrast of the fringe target accurately. The light entrance window of the light receiving element 15 is equal to or less than の of the stripe pitch. Although it is not indispensable that the pitch is not more than 1/2, it is preferable that the pitch is not more than 1/2 of the stripe pitch in order to simplify the processing.

Next, a description will be given of a main part of an electric system for driving the present apparatus, which is divided into a calibration mechanism for maintaining the contrast accurately and a mechanism for examining the eye to be inspected. FIG. 3 is an electric block diagram of the calibration mechanism. The fringe target plate 7 is moved by the fringe target driving unit 8 to project the bright part and the dark part of the fringe target sequentially, and each luminance (light amount) is measured. The light incident on the light receiving element 15 is converted into an electric signal and amplified by the amplifier 16. The amplified signal is converted into a digital signal by an A / D converter 17 and then input to a micro computer 18.
Microcomputer (also controls the operation of the entire device) 1
8, the contrast is calculated from the brightness of the bright part and the dark part. The contrast is expressed by the following equation. Here, A is the luminance of the bright part of the stripe pattern, and B is the luminance of the dark part of the stripe pattern (the luminance of the adaptation field).

The microcomputer 18 compares the contrast obtained in this way with a specified value, and instructs the PWM pulse generator 19 to brighten the halogen lamp 1 when it is small and darken it when it is large. Generate a pulse signal. Lamp driver 2 based on pulse signal
0 controls the voltage applied to the halogen lamp 1.

FIG. 4 is an electrical block diagram for controlling the operation for examining the eye to be inspected (the illumination circuit of the halogen lamp 1 is omitted since it is shown in FIG. 3). The microcomputer 18 controls on / off of the halogen lamp 14 via the lamp driver 21, driving of the pulse motor 5 via the motor driver 22, and driving of the stripe target driving unit 8 via the motor driver 23. . The signal from the patient response switch 24 is input to the microcomputer 18 for processing. Reference numeral 25 denotes a printer driver that outputs an inspection result, and reference numeral 26 denotes a printer. 27 is a control
And specifies the contrast and the presentation speed.

[0019]motion  The operation of the apparatus according to the embodiment having the above-described configuration will be described.
The description will be made based on the chart. Figure 5 shows the contrast
This is a calibration flowchart. Device power
When the power switch (not shown) is turned on, the halogen lamp
1 and 14 are turned on, and the pulse motor 5
The disc 4 is set at the initial position. To the stripe target drive unit 8
The fringe target plate 7 is further moved, and the bright part and the dark part of the fringe target are sequentially examined.
Project onto the light entrance window and measure the brightness of each projected light
(Step 1-1). Based on the measured brightness of the projected light
To calculate the contrast (step 1-2).
Is compared with a predetermined value (step 1-3).
If the error between the two is within the specified range, the calibration
End. If the error is outside the specified range,
Of the halogen lamp 1 (step 1-4).
Increase or decrease the applied voltage at predetermined steps (step
P 1-5, 1-6). Such an operation has an error with the specified value.
This is repeated until the value falls within the predetermined range.

FIG. 6 is a flowchart of the inspection. When the examination is started, first, the subject's eye is caused to look at the screen for 1-2 minutes (step 2-1). This is to make the eye to be examined light-adapted. Next, the disk 4 is driven to set the contrast of the fringe target to 10% (step 2-).
2), the count of the inspection loop is set to 0 (step 2-3). Here, one loop represents one kind of inspection using one contrast.

When this step is completed, the examiner presses the start switch of the controller 27, and thereafter the measurement is automatically performed. Present a stationary fringe target (Step 2-
4) The subject is made to respond whether or not the striped target can be visually recognized by the subject's eye (Step 2-5). If the response is correct, the process proceeds to Step 2-6, and if the response is incorrect, Step 2-7.
Proceed to.

In step 2-6, the controller 27 is operated to vibrate the striped optotype plate 7 so that the examinee responds (step 2-8). Proceed to step 2-9. If the response is incorrect, the process proceeds to step 2-7.

In step 2-9, the contrast of the fringe target is reduced by one step. It is determined whether the contrast lowered by one stage is the lowest contrast (step 2-10). If the contrast is the lowest, step 2 is performed.
Proceed to -11.

If the contrast is not minimum, the inspection rule
It is determined whether the count of the loop is 10 or more (step 2-12). If the detection result to be obtained is obtained when the number of inspection loops is 10 or more, the process proceeds to step 2-11.

If the number of inspection loops is less than 10, it is determined whether or not the change width of the contrast is 0.1% or less (step 2-13). If it is 0.1% or less, it is determined that the inspection result is correct, and the process proceeds to step 2-11. 0.
If not less than 1%, the count of the inspection loop is incremented by 1 and the process proceeds to A (step 2-14).

On the other hand, in step 2-7, the contrast is increased by one-half step, and the process proceeds to 2-15, where it is determined whether or not the contrast is the maximum value. If not, the process proceeds to step 2-12.

In step 2-11, the inspection result is printed out. It has been clinically confirmed that the test result is normal if the contrast is 1% or less, and abnormal if the contrast is higher than 1%.

Although the above-described measurement is a measurement in the auto mode, the method of setting the contrast and the like by the examiner may be adopted. Further, the inspection can be repeated several times while changing the direction of the stripe, and the accuracy can be increased by a method of obtaining an average of the measured values.

In the embodiment described above, the contrast is switched by switching the disk 4 arranged in the fringe target projection optical system. However, the contrast can be switched by adjusting the light amount of the projection light source itself. it can. Instead of calibrating the contrast by adjusting the amount of light of the halogen lamp 1, the halogen lamp 1
4 may be adjusted, or control data of the disk 4 may be converted. As described above, the present embodiment can be variously modified, and these modifications are included in the present invention as long as the technical idea is the same.

[0030]

According to the moving object detection contrast threshold value inspection apparatus of the present invention, an optotype having an accurate contrast value can always be presented to the subject, and visual field impairment due to the onset of glaucoma, diabetic retinopathy and the like can be achieved. Early abnormalities can be found.

[Brief description of the drawings]

FIG. 1 is an optical system layout diagram showing a configuration of an optical system of an inspection apparatus according to the present embodiment.

FIG. 2 is an explanatory diagram of a stripe target.

FIG. 3 is an electrical block diagram of the calibration mechanism.

FIG. 4 is an electrical system block diagram for controlling an operation for examining an eye to be inspected.

FIG. 5 is a flowchart of calibration of contrast.

FIG. 6 is an inspection flowchart.

[Explanation of symbols]

 1,14 Halogen lamp 2 Condenser lens 3,9 Aperture 4 Disk 5 Pulse motor 6,10 Projection lens 7 Stripe target plate 8 Stripe target drive unit 11,12 Mirror 13 Screen 15 Light receiving element

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) A61B 3/028 A61B 3/024

Claims (4)

(57) [Claims] 1. A fringe target projection optical system for projecting a fringe target on a projection screen, contrast switching means for switching the contrast of the fringe target, a drive unit for oscillating the fringe target, and the projection An illumination optical system for illuminating the screen substantially uniformly; a photodetector arranged near the projection screen for detecting the amount of light; an illumination optical system and a fringe target based on an output from the photodetector; A moving object detection contrast threshold value inspection apparatus, comprising: an adjustment unit that adjusts the light amount of at least one light source in the projection optical system. 2. The contrast switching means according to claim 1, wherein said contrast switching means is a switchable filter arranged in said fringe target projection optical system or a switch means for adjusting a light amount of a projection light source of said fringe target. Moving object detection contrast threshold inspection apparatus. 3. The moving object detection contrast threshold value inspection apparatus according to claim 1, wherein the photodetector according to claim 1 is disposed substantially at the center of the stripe target projected on the projection screen and used as a fixation target. 4. A photodetector for detecting the amount of light according to claim 1, further comprising a light receiving window smaller than each width of a bright portion and a dark portion of the projected fringe target, and moving the fringe target by moving the fringe target. And detecting the light amounts when the bright and dark portions cover the light receiving window, and adjusting the light amount of the light source based on the detected light amounts.