JPH0738847B2 - Eye movement detection method and doze detection / prevention device - Google Patents

Description

The present invention relates to a method for detecting eye movements and a doze detection / prevention apparatus to which the method is applied.

[Prior Art] Conventionally, as a drowsiness preventive device for a driver of a vehicle or the like, a drowsiness for detecting a driver's drowsiness state and detecting a drowsiness state by detecting an action potential of a retinal photoreceptor cell or a head tilt angle. Prevention devices have been proposed.

[Problems to be Solved by the Invention] However, the above-mentioned conventional drowsiness preventive device detects the driver's drowsiness after it has already entered the drowsiness state, so the warning time is too late and an accident occurs before the warning. There was a risk of occurrence.

On the other hand, in addition to the above-mentioned drowsiness prevention device, there has been a demand in the medical field or the like to accurately grasp the awakening level of the subject's consciousness. To detect the level of consciousness, it is possible to discriminate the EEG, but to detect and discriminate the EEG, a lot of troublesome electrode adhesion to the scalp and a large-scale circuit device are required. It was not practical for applications such as when monitoring a car or when a general driver easily used it.

In addition, it has been known that there is a deep correlation between the fluctuation of the consciousness arousal level and the fluctuation of the eye movement pattern, and it is known that the consciousness arousal level can be grasped from the eye movement. There was no specific proposal for a method that enables faithful and highly sensitive detection of.

The present invention has been made in view of such a problem, and it is an object to be solved to provide a faithful and high-sensitivity detection method of eye movements by a simple method, and a dozing prevention device to which the method is applied. It is a thing.

[Means for Solving the Problems] In the eye movement detecting method of the present invention, a magnetic sensor is attached to a spectacle-shaped support frame so as to face the eyelid by interlocking a minute permanent magnet with the eyelid, and the magnetic sensor The feature is that the movement of the eyelids is detected in a non-contact manner by detecting the magnetic field change from the permanent magnet.

The drowsiness detection / prevention device of the present invention discriminates the awakening level of a subject from a permanent magnet in contact with an eyelid, a magnetic sensor arranged on an eyeglass-shaped support frame, and an eyelid motion state detected by an output signal of the magnetic sensor. And a warning means for warning the subject when the decrease in the awakening level is detected.

The permanent magnet can have various shapes such as a magnetic tape shape, a small thin piece shape, a wire shape, a needle shape, and a rubber magnet plate shape.

As the magnetic sensor, various types from a semiconductor magnetic sensor to an amorphous magnetic sensor can be used as long as they detect a change in magnetic field strength due to a change in relative distance between the permanent magnet and the magnetic sensor and finally convert it into an electric signal. Can be adopted.

For example, the magnetic sensor may be of a type in which the magnetic permeability of the magnetic core is changed by the change of the magnetic field and the inductance change of the coil wound around the magnetic core is detected. The inductance of this coil can be detected by a known method as a change in voltage or current or a change in oscillation frequency.

[Operation] As described above, there is a deep correlation between the fluctuation of the arousal level of consciousness and the fluctuation of the pattern of eye movement, and it is also known that the eyeball is interlocked with the eyelid. The eyelid movement more sensitively reflects the mental state of the subject than the eye movement, and thus the eyelid movement detection can be said to be the most suitable method for detecting the arousal level.

Therefore, in the drowsiness detection / prevention device of the present invention, the movement of the eyelids is detected by the magnetic field change of the permanent magnets interlocking with the eyelids by the magnetic sensor arranged on the spectacle-shaped support frame. Then, the discriminating means discriminates the half awakening level before entering the drowsy level by obtaining the eye movement pattern peculiar to the half awakening level from the detected eyelid movement, and drives the warning means to warn before entering the drowsy state. To do.

[First Embodiment] A first embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, this drowsiness detection / prevention device includes a pair of permanent magnets 1 and 2 bonded to both eyelids a and b, and a pair of magnetic sensors 4 and 5 fixed to an eyeball support frame 3. A signal processing discriminating device 6 that discriminates the awakening level of the subject from the eyelid motion state detected by the output signals of the magnetic sensors 4 and 5, and an alarm means 7 that warns the subject when a decrease in the awakening level is detected. .

The permanent magnets 1 and 2 are each composed of a small disk-shaped rare earth magnet having a diameter of 2 mm and an axial length of about 2 mm, and as shown in FIGS. 2 and 3, adhered to the center of both eyelids with a double-sided tape 11. Has been done. The permanent magnets 1 and 2 have an S-pole on the bottom surface side which is bonded,
The opposite top surface side is magnetized to the N pole.

As shown in FIG. 4, each of the magnetic sensors 4 and 5 comprises a plurality of detection elements, 40 and 50, and detectors 41 and 51 for detecting the inductance change of the detection elements 40 and 50. Detection element 40, 50
2 is arranged on a transparent plate 30 provided on the spectacle support frame 3 as shown in FIGS. 2 and 3, and can be normally measured while wearing glasses. A gap between the permanent magnets 1 and 2 and the detection elements 40 and 50 is arranged at about 10 mm. The detecting elements 40 and 50 were adjusted to magnetic strain as shown in FIG.
Co-based amorphous magnetic cores 42 and 52 are wound with a predetermined number of turns, and both ends of each coil are connected to the input ends of detectors 41 and 51 embedded in the spectacle support frame 3.
Each of the amorphous magnetic cores 42 and 52 has a plurality of permanent magnets 1,
The coils are arranged in a radial pattern centered at 2, and the coils are connected in series. As a result, the earth's magnetism and the disturbance magnetic field in the vehicle body are canceled out in the entire magnetic core, so that even minute vibrations of the magnet up to 0.02 μm can be detected. Detectors 41 and 51 are detection elements
It is composed of a differential amplifier that linearly amplifies the inductance change of 40 and 50. The amorphous magnetic cores 42 and 52 are formed to have a diameter of about 0.4 mm and an axial length of about 4 mm.

The signal processing discriminating device 6 is housed in the compact case 8 together with the alarm device 7, and is connected to each output end of the detectors 41 and 51 by signal lines 91 and 92. A compact battery E is built in the compact case 8, and the battery E supplies the power supply voltage to the detectors 41 and 51 via the power supply line 90 together with the signal processing determination device 6 and the alarm device 7. As shown in FIG. 4, the signal processing discriminating device 6 includes pre-processing circuits 61 and 62 for A / D converting the signal voltages V1 and V2 output from the magnetic sensors 4 and 5 after high-frequency interruption. It comprises a microcomputer 60 which processes the digital signals D1 and D2 output from the processing circuits 61 and 62 and outputs a drowsiness alarm signal S.

The alarm device 7 is composed of an electronic buzzer which keeps ringing unless it receives a doze alarm signal S and is manually turned off.

It should be noted that these detectors, signal processing units, batteries, etc. are sufficiently miniaturized by the hybrid IC technology and can be mounted on both side frames of all glasses. Therefore, the driver can very easily prevent falling asleep by simply bonding the small magnets to both eyelids and wearing the glasses with the sensor.

The operation of the drowsiness detection / prevention device will be described below.

The permanent magnet 1 works together with the right eyelid a and the permanent magnet 2 works together with the left eyelid b, and the inductance of the magnetic sensor 4 changes due to a change in the magnetic field strength associated with the displacement of the permanent magnet 1 especially in the vertical direction, and the inductance of the magnetic sensor 5 becomes permanent. Magnet 2
Changes due to the change in the magnetic field strength that accompanies the vertical displacement. The change in inductance of the magnetic sensor 4 is converted into a change in voltage by the detector 41, and after being amplified by about 60 to 80 db,
After the high frequency component is cut off by the preprocessing circuit 61, it is A / D converted and transmitted to the microcomputer 60. Similarly, the inductance change of the magnetic sensor 5 is converted into a voltage change by the detector 42, amplified, and then converted into A / D after the high frequency component is cut off by the preprocessing circuit 62 and transmitted to the microcomputer 60.

The microcomputer 60 performs arithmetic processing on the digital signals D1 and D2 using a built-in data processor to obtain a cross-correlation function value Dm. The cross-correlation function value Dm is the digital signal D1 and
It represents the correlation value between the same time values of D2.

To explain the above arithmetic processing in detail, first, one of the digital signals D1 is multiplied and complemented so that the maximum amplitudes of the digital signals D1 and D2 in a predetermined period (-0.5 sec to +0.5 sec) over the present time tχ are equal. Stop. Next, the difference between the two digital signals D1 and D2 is obtained while shifting the time axis of one of the digital signals D1 within the predetermined period. In other words, each difference between each of the numerical values (D1i to D1n) of a large number of digital signals D1 sampled at equal intervals in the above-mentioned predetermined period and each of the digital signals D2 at the present time tχ is obtained. Next, the obtained differences are squared and then added to obtain the cross-correlation function value Dm of the present time tχ. 5 to 7 show waveforms of the signal voltages V1 and V2 output from the magnetic sensors 4 and 5, respectively. However, FIG. 5 shows the awake state, FIG. 6 shows the half awake state before dozing, and FIG.
The figure shows a dozing state. It should be noted that FIG. 6 is extended about 28 times in the vertical direction from FIG. 5, and FIG. 7 is extended about 36 times in the vertical direction from FIG. FIG. 8 shows the relationship between the cross-correlation function value Dm and the arousal level of consciousness. As can be seen from FIG. 8, the correlation (cross-correlation function value Dm) between the two digital signals D1 and D2 decreases as the consciousness arousal level decreases.

In this embodiment, the microcomputer 60 outputs a drowsiness alarm signal S to the alarm device 7 when the cross-correlation function value Dm becomes less than or equal to a predetermined threshold level Th, and the alarm device 7 sounds to alert the driver. Give a warning.

According to this drowsiness detection / prevention device, the correlation between the movements of both eyelids decreases with a decrease in the wakefulness level of consciousness, thereby detecting a half-awakening state before falling asleep and activating an alarm device. Therefore, it is useful for accident prevention.

Second Embodiment Another embodiment of the doze detection / prevention device of the present invention is shown in FIGS. 9 and 10.

This drowsiness detection / prevention device is a permanent magnet 1a supported by a spectacle-shaped support frame 3a, a magnetic sensor 4a fixed to the spectacle-shaped support frame 3a, and an eyelid motion state detected by an output signal from the magnetic sensor 4a. From the signal processing discriminating device 6a for discriminating the awakening level of the subject, an alarm device 7a that warns the subject when a decrease in the arousal level is detected, and an FM for wirelessly connecting the magnetic sensor 4a and the signal processing discriminating device 6a. The modulator 8a, the transmitter 8b, the receiver 8c, and the FM detector 8d are provided.

On the rear part of the spectacles-shaped support frame 3a, a resin-made protrusion 32 having a built-in magnetic sensor 4a is arranged by integral molding with the spectacles-shaped support frame 3a, and is provided on the top surface of the resin-made protrusion 32. One end of an L-shaped small-sized elastic frame 33 made of resin is fitted into the formed support hole (not shown). The other end of the resin elastic frame 33 extends downward, and a resin thin plate 34 is attached to the tip thereof.
Is stuck. At the corners of the resin elastic frame 33,
The same permanent magnet 1a as the permanent magnet 1 of Example 1 has a resin protrusion.
The permanent magnet 1a is erected toward 32 and the bottom side is S
The pole and the opposite top surface side are magnetized to the N pole. The resin elastic frame 33 is formed of a resin material having high elasticity, and the resin elastic frame 33 bends to some extent when the subject wears the spectacle-shaped support frame 3a, and the resin thin plate 34 is placed on one eyelid a. It is pressing lightly. As a result, the resin thin plate 34 has a roughened surface and adheres well to the eyelids, so that it interlocks with the eyelids.

As shown in FIG. 10, the magnetic sensor 4a has a diameter of 120 μm.
The detection element 40a has an axial length of 4 mm, and the detector 41a detects an inductance change of the detection element 40a. The detection element 40a is made of resin 32 so that it is close to the permanent magnet 1a.
The detector 41a is embedded in the end of the spectacle-shaped support frame 3a. The detection element 40a is configured by winding the coil 43a around the amorphous high magnetostrictive wire 42a by a predetermined number of turns, and both ends of each coil are connected to the input end of the detector 4c. The detection element 40a is formed by melting molten Fe77.5Si7.5B15 by an underwater quenching method, and has a function of generating a sharp pulse voltage even with an AC magnetic field of about 0.20e.
The detector 41a is a sense amplifier that amplifies the pulse voltage induced in the detection element 40a. Further, the detector 41a supplies a predetermined current to the coil 43a so that the amorphous high magnetostrictive wire 42a generates a pulse voltage with respect to a certain amount of displacement of the permanent magnet 1a, and an internal bias magnetic field of the amorphous high magnetostrictive wire 42a. It also contains a variable bias current supply circuit source that adjusts the.

The FM modulator 8a and the transmitter 8b are built in the eyeglass-shaped support frame 3a together with the small battery, and the receiver 8c and the FM detector 8d are included.
Is contained in a compact case (not shown) together with the signal processing determination device 6a and the alarm device 7a. The signal processing discrimination device 6a is composed of a microcomputer with an A / D converter built-in.

Next, the operation of this drowsiness detection / prevention device will be described.

A pulse voltage is generated in the detection element 40a due to the displacement of the permanent magnet 1a which is interlocked with the eyelid a above a predetermined level.

On the other hand, as shown in FIGS. 5 to 7, the amplitude in the awake state is much larger than that in the half awake state, and the amplitude in the half awake state is larger than that in the doze state. In this embodiment,
The coil 43a is energized so that the magnetic field change such that the detection element 40a generates a pulse voltage to such an extent that it rarely occurs in the semi-wake state and frequently occurs in the wake state in the amorphous high magnetostrictive wire 42a due to the movement of the permanent magnet. The bias current is adjusted. The pulse voltage generated from the detection element 40a is amplified by the detector 41a and is FM-generated by the FM modulator 8a.
It is converted into a signal and transmitted from the transmitter 8b. The FM signal received by the receiver 8c is detected by the FM detector 8d and then output to the signal processing determination device 6a. The signal processing discriminating device 6a counts the number of pulses per predetermined period, and outputs a doze alarm signal S to the alarm device 7a when the counted number exceeds a predetermined threshold value.

According to this embodiment, only one pair of the permanent magnet 1a and the magnetic sensor 4a needs to be provided, and the signal processing determination device 6a is further provided.
Only counts the number of pulses and judges whether the count value exceeds a predetermined threshold value within a predetermined time, so that the configuration is simple. The signal processing discrimination device 6a can be replaced with hardware having a comparator and a counter.

[Effects of the Invention] As described above, in the eye movement detecting method of the present invention, the movement of the permanent magnet interlocking with the eyelids is detected by the magnetic sensor fixed to the spectacle-shaped support frame. And it can be detected with high sensitivity.

Further, the doze detection / prevention device of the present invention is configured to detect and warn a decrease in the wakefulness level of consciousness from the change in the state of eye movement detected by the above method, so that the subject does not enter the dozing state. It is especially useful from the perspective of accident prevention.

[Brief description of drawings]

FIG. 1 is a schematic front view showing a first embodiment of the doze detection / prevention device of the present invention, FIG. 2 is a partial schematic plan view of FIG. 1, and FIG. 3 is a schematic sectional side view of FIG. FIG. 4 is a block diagram of the embodiment of FIG. 1, FIG. 5, FIG. 6, and FIG. 7 are waveform diagrams of signals V1 and V2 at each awakening level, and FIG. 8 is a cross-correlation signal value Dm at each awakening level. FIG. 9 is a schematic sectional side view showing a second embodiment of the doze detection / prevention device of the present invention, and FIG. 10 is a block diagram of the second embodiment. 1, 2 ... Permanent magnets 3 ... Eyeglass-shaped support frame 4, 5 ... Magnetic sensor 6 ... Signal processing discriminating device (discriminating means) 7 ... Warning device (warning means)

Claims (2)

[Claims] 1. A permanent magnet is interlocked with an eyelid, and a magnetic sensor is attached to an eyeglass-shaped support frame so as to face the eyelid,
A method for detecting eye movement, wherein the magnetic sensor detects a magnetic field change from a permanent magnet to detect eyelid movement. 2. A permanent magnet in contact with the eyelid, a magnetic sensor arranged on the spectacle-shaped support frame, and a discriminating means for discriminating the awakening level of the subject from the motion state of the eyelid detected by the output signal of the magnetic sensor. A drowsiness detection / prevention device comprising: alarm means for warning a subject when the decrease in the awakening level is detected.