JPH02220627A - Method for detecting motion of eyeball and apparatus for detecting and preventing doze - Google Patents

Abstract

PURPOSE:To faithfully detect the motion of an eyeball interlocking to an eyelid by linking a fine permanent magnet to the eyelid and mounting a magnetic sensor to a glasses-shape support frame in opposed relation to the eyelid and detecting a change of the magnetic field from the permanent magnet by the magnetic sensor to detect the motion of the eyelid in a non-contact state. CONSTITUTION:A permanent magnet 1 interlocks along with a right eyelid (a) while a permanent magnet 2 interlocks along with a left eyelid (b) and the inductance of a magnetic sensor 4 is changed by the intensity change of a magnetic field accompanied by the displacement of the permanent magnet 1 especially in a vertical direction and that of a magnetic sensor 5 is changed by the intensity change of a magnetic field accompanied by the displacement of the permanent magnet 2 especially in a vertical direction. The inductance change of the magnetic sensor 5 is converted to a voltage change by a detector 41 to be amplified by about 60-80 db and, after a high band component is cut off by a pre-processing circuit 61, the amplified voltage change is converted to a digital value by an A/D converter to be transmitted to a microcomputer 60. The microcomputer 60 outputs a doze alarm signal S to an alarm apparatus 7 when a cross-correlation function value Dm becomes a predetermined threshold value level Th or less and the alarm apparatus 7 emits sound to give warning to a driver.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting eye movement and a dozing detection/prevention device using the method.

[Prior Art] Conventionally, a dozing prevention device for drivers of automobiles, etc. detects the driver's dozing state by detecting the action potential of retinal photoreceptor cells and detecting the head tilt, and warns the driver of dozing off. Prevention devices have been proposed.

[Problems to be Solved by the Invention] However, the above-mentioned conventional dozing prevention device detects the driver after the driver has already fallen asleep, so the warning time is too late and the accident occurs before the warning is given. There was a risk that this would occur.

On the other hand, in the medical field, etc., there has been a demand for the above-mentioned dozing prevention device to accurately grasp the arousal level of a subject's consciousness. It is possible to detect the alertness level of consciousness by distinguishing brain waves, but detecting and distinguishing brain waves requires a large number of troublesome electrodes attached to the scalp and a large-scale circuit device. This was not practical for purposes such as monitoring traffic or being easily used by general drivers.

Furthermore, it has long been known that there is a deep correlation between fluctuations in the level of conscious arousal and fluctuations in eye movement bang, and it is known that the level of conscious arousal can be determined from eye movements, but eye movement There have been no concrete proposals regarding methods that enable faithful and sensitive detection of .

The present invention was made in view of these problems, and an object to be solved is to provide a method for detecting eye movements with high fidelity and high sensitivity using a simple method, and a dozing prevention device applying the method. It is something.

[Means for Solving the Problems] In the eye movement detection method of the present invention, a minute permanent magnet is interlocked with the eyelid, a magnetic sensor is attached to a spectacle-like support frame so as to face the eyelid, and the magnetic sensor detects the movement of the eyeball. It is characterized by non-contact detection of eyelid movement by detecting changes in the magnetic field from a permanent magnet.

The drowsiness detection/prevention device of the present invention uses a permanent magnet in contact with the eyelid, a magnetic sensor disposed on a spectacle-shaped support frame, and the state of eyelid movement detected by the output signal of the magnetic sensor to determine the arousal level of the subject. and an alarm means for warning the subject when a decrease in the arousal level is detected.

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

Magnetic sensors can be of various types, from semiconductor magnetic sensors to amorphous magnetic sensors, as long as they detect changes in magnetic field strength due to changes in the relative distance between a permanent magnet and a magnetic sensor, and ultimately convert it into an electrical signal. can do.

For example, a magnetic sensor may be of a type that changes the magnetic permeability of a magnetic core by changing the magnetic field and detects changes in the inductance of a coil wound around the magnetic core. The inductance of this coil can be detected in known ways as a change in voltage or current or a change in firing frequency.

[Effect] As described above, there is a deep correlation between fluctuations in the level of arousal and fluctuations in eye movement, and it is also known that the eyeballs are linked with the eyelids. Furthermore, eyelid movement reflects the subject's mental state more sensitively than eyeball movement, and detection of eyelid movement can be said to be the most suitable method for detecting arousal level.

Therefore, in the drowsiness detection/prevention device of the present invention, movement of the eyelids is detected by a magnetic sensor disposed on the spectacle-shaped support frame based on a change in the magnetic field of a permanent magnet interlocked with the eyelids. Then, the determining means determines the semi-awake level before entering the dozing state by determining the eye movement slam peculiar to the semi-awake level from the detected eyelid movement, and drives the alarm means to warn before entering the dozing state. do.

[Example] (First Example) An example of the dozing detection/prevention device of the present invention will be described with reference to the drawings.

As shown in FIG. 1, this dozing detection/prevention device includes a pair of permanent magnets 1.2 glued to both eyelids a and b, and a pair of magnetic sensors 4.5 fixed to a spectacle-shaped support frame 3. , a signal processing and discriminating device 6 that determines the subject's arousal level from the eyelid movement state detected by the output signal of the magnetic sensor 4.5, and an alarm means 7 that warns the subject when a decrease in the arousal level is detected. Become.

Each of the permanent magnets 1.2 is composed of a small disk-shaped rare earth magnet with a diameter of 2 mm and an axial length of about 2 mm, and is attached to the center of both eyelids with double-sided tape 11, as shown in FIGS. 2 and 3. has been done. The permanent magnet 1.2 is magnetized so that the bottom side to which it is bonded is an S pole, and the opposite top side is magnetized to an N pole.

As shown in FIG. 4, each magnetic sensor 4.5 includes a plurality of detection elements 40.50 and a detector 41.51 that detects changes in inductance of the detection elements 40.50. As shown in FIGS. 2 and 3, the detection elements 40 and 50 are arranged on a transparent plate 30 provided on the eyeglass support frame 3,
Measurements can usually be taken while wearing glasses. The distance between the permanent magnet 4.5 and the detection elements 40 and 50 is approximately 1 Qmm.
It is set to about. As shown in FIG. 4, the detection element 40.50 is made by winding a coil a predetermined number of turns around a Co-based amorphous magnetic core 42.52 adjusted to zero magnetostriction, and both ends of each coil are connected to the eyeglass support frame 3. It is connected to the input end of a detector 41.51 embedded in the. A plurality of amorphous magnetic cores 42, 52 are each arranged in a radial pattern around the permanent magnet 1.2, and each coil is connected in series. As a result, earth's magnetism and disturbing magnetic fields inside and outside the vehicle body are canceled out within the entire magnetic core, making it possible to detect minute movements of the magnet down to 0.02 μm. The detector 41.51 is composed of a differential amplifier that linearly amplifies the inductance change of the detection element 40.50. Amorphous magnetic core 4
2.52 has a diameter of about 0.4 mm and an axial length of about 4 mm.

The signal processing discrimination device 6 is housed in a compact case 8 together with the alarm device 7, and is connected to each output end of the detector 41.51 by signal lines 91.92. Also,
The compact case 8 has a built-in small battery E, and the battery E is connected to the signal processing and discrimination device 6 and the alarm device 7.
At the same time, a power supply voltage is supplied to the detector 41.51 via a power supply line 90. As shown in FIG. 4, the signal processing discrimination device 6 receives the signal l pressure V output from the magnetic sensor 4.5.
After the LV2 is cut off by 11!1 m, the pre-processing circuit 61.62 performs A/D conversion, and the digital signals D1 and D2 output from the pre-processing circuit 61.62 are processed to generate the dozing alarm signal S. It consists of a microcomputer 60 that outputs.

The alarm device 7 consists of an electronic buzzer that continues to sound unless it is turned off manually upon receiving the dozing alarm signal S.

Note that these detectors, signal processing units, batteries, etc. have been sufficiently miniaturized using hybrid IC technology, and can all be attached to both side frames of eyeglasses. Therefore, drivers can easily prevent falling asleep by simply attaching micromagnets to both eyelids and wearing sensor-equipped glasses.

The operation of this doze detection/prevention device will be explained below.

The permanent magnet 1 moves with the right eyelid a, and the permanent magnet 2 moves with the left eyelid b. The inductance changes due to a change in magnetic field strength as the permanent magnet 2 is displaced, particularly in the vertical direction. The change in inductance of the magnetic sensor 4 is detected by the detector 41.
After the signal is converted into a voltage change and amplified by about 60 to 80 db, the preprocessing circuit 61 cuts off high frequency components ffti, A/D converts it, and transmits it to the microcomputer 60. Similarly,
The inductance change of the magnetic sensor 5 is converted into a voltage change and amplified by the detector 42, and then A/D converted by the preprocessing circuit 62 after cutting off high frequency components and transmitted to the microcomputer 60.

The microcomputer 60 processes the digital signals D1 and D2 using a built-in data processor, and obtains a cross-correlation function value [).
Find m. Note that this cross-correlation function value [)m represents the correlation value between the values of the digital signals D1 and D2 at the same time.

To explain the above calculation process in detail, first, a predetermined period (-0,5 sec to 10Q, 5 sec) around the current time tχ
One of the digital signals D1 is subjected to multiplicative correction so that the maximum amplitudes of the digital signals D1 and D2 at > are equal.

Next, the time axis of one digital signal D1 is shifted within the predetermined period, and the difference between the two digital signals D1 and D2 is determined.

In other words, each numerical value (D11 to D1
n> and the digital signal D2 at the current time tχ. Next, the obtained winter clothes are squared and then added to obtain the cross-correlation function value Dm of the current time tχ. The signal voltage v output from the magnetic sensor 4.5 is shown in Figures 5 to 7.
1. Shows the waveform of V2. However, FIG. 5 shows an awake state, FIG. 6 shows a semi-awake state before dozing off, and FIG. 7 shows a dozing state. Note that FIG. 6 is about 28 times longer than FIG. 5 in the vertical direction, and FIG. 7 is about 36 times longer than FIG. 5 in the vertical direction. FIG. 8 shows the relationship between the cross-correlation function value Dm and the level of conscious arousal.

As can be seen from FIG. 8, the correlation between the two digital signals D1 and D2 (cross-correlation function value Dm) decreases as the arousal level of consciousness decreases.

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

This dozing detection/prevention device detects a semi-awake state before falling asleep by utilizing the fact that the correlation between the movements of both eyelids decreases as the alertness level decreases, and activates an alarm device. This is useful for preventing accidents.

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

This dozing detection/prevention device uses 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 movement state detected by the output signal of the magnetic sensor 4a. A signal processing discrimination device 6a that discriminates the arousal level of the subject, an alarm device 7a that warns the subject when a decrease in the arousal level is detected, and FM modulation for wirelessly connecting the magnetic sensor 4a and the signal processing discrimination device 6a. transmitter 8a, transmitter 8b, receiver 8C, F
It is equipped with an M detector 8d.

At the rear of the spectacle-shaped support frame 3a, a resin protrusion 32 containing a magnetic sensor 4a is provided by integral molding with the spectacle-shaped support frame 3a, and a hole is formed on the top surface of the resin protrusion 32. One end of a single-shaped, small-diameter resin elastic frame 33 is fitted into the support hole (not shown). The other end of the resin elastic frame 33 extends downward, and a thin resin plate 34 is fixed to the tip thereof. At the corner of the resin elastic frame 33, a permanent magnet 1a, which is the same as the permanent magnet 1 of Example 1, is erected toward the resin protrusion 32, and the permanent magnet 1a has an S pole on the bottom side and an S pole on the opposite top. The surface side is magnetized to the north pole. The resin elastic frame 33 is made of a highly elastic resin material, and allows the subject to hold the eyeglass-shaped support frame 3a.
In the state in which the eyelid is worn, the resin elastic frame 33 bends to a certain extent and lightly presses the resin thin plate 34 against one eyelid a. As a result, the thin resin plate 34 has a roughened surface, adheres well to the eyelid, and moves in conjunction with the eyelid.

The magnetic sensor 4a has a diameter of 12 mm as shown in FIG.
A detection cable 40a having an axial length of 0 μm and 4 mm, and a detector 41a that detects changes in inductance of the detection cable 40a.
It consists of The detection cable 40a is embedded in the resin protrusion 32 so as to be close to the permanent magnet 1a, and the detector 4
1a is built into the end of the spectacle-shaped support frame 3a. The detection element 40a is constructed by winding a coil 43a around an amorphous high magnetostriction wire 42a for 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 composed of molten Fe77°5, s*7.5,
It is molded from B15 using an underwater quenching method, and has a diameter of 0.20e.
It has the ability to generate sharp pulse voltages even in the presence of moderate alternating magnetic fields. The detector 41a is a sense amplifier that amplifies the pulse voltage induced in the detection element 40a. In addition, the detector 41a supplies a predetermined current to the coil 43a so that the amorphous high magnetostrictive wire 42a generates a pulse voltage in response to displacement of the permanent magnet 1a above a certain level, and generates an internal bias magnetic field of the amorphous high magnetostrictive wire 42a. It also has a built-in variable bias current supply circuit source that adjusts the current.

The FM modulator 8a and the transmitter 58b are built into the spectacle-shaped support frame 3a together with a small battery, and the receiver 8C and the FM detector 8d are integrated into the signal processing and discrimination device 6a and the alarm device 7.
It is housed in a compact case (not shown) together with a. The signal processing discrimination device 6a is composed of a microcomputer with a built-in A/DD converter.

Next, the operation of this doze detection/prevention device will be explained.

A pulse voltage is generated in the detection element 40a by displacement of the permanent magnet 1a interlocked with the eyelid a by a predetermined amount or more.

On the other hand, as shown in FIGS. 5 to 7, the amplitude in the awake state is much larger than in the semi-awake state, and the amplitude in the semi-awake state is larger than in the dozing state. In this example,
The magnetic field is applied to the coil 43a so that the movement of the permanent magnet causes a magnetic field change in the amorphous high magnetostrictive wire 42a such that the detection element 40a generates a pulse voltage, which occurs only occasionally in the semi-awake state but occurs frequently in the awake state. The applied bias current is adjusted. Detection element 40
The pulse voltage generated from a is amplified by the detector 41a and
It is converted into an FM signal by the M modulator 8a 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 and discrimination device 6a. The signal processing discrimination device 6a counts the number of pulses per predetermined period, and outputs a dozing alarm signal S to the alarm device 7a when the counted number exceeds a predetermined threshold.

According to this embodiment, it is sufficient to provide only one pair consisting of the permanent magnet 1a and the magnetic sensor 4a, and furthermore, the signal processing discrimination device 6a counts the number of pulses, and the count value is set to a predetermined threshold value during a predetermined time. Since it is only necessary to judge whether or not the value exceeds , the configuration is simple. In addition, the signal processing discrimination device 6
a can also be replaced by hardware having a comparator and a counter.

[Effects of the Invention] As explained above, the eye movement detection method of the present invention detects the movement of the permanent magnet in conjunction with the eyelids using a magnetic sensor fixed to the spectacle-like support frame, so that the eye movement in conjunction with the eyelids can be accurately detected. And it can be detected with high sensitivity.

Furthermore, the dozing detection/prevention device of the present invention is configured to detect and warn a decrease in the alertness level from the change in the state of eye movement detected by the above method, so that it can be detected before the subject falls into a dozing state. This is particularly useful from the perspective of accident prevention.

[Brief explanation of the drawing]

Fig. 1 is a schematic front view showing a first embodiment of the dozing detection/prevention device of the present invention, Fig. 2 is a partial schematic plan view of Fig. 1, and Fig. 3 is a schematic cross-sectional side view of Fig. 1; FIG. 4 is a block diagram of the first embodiment, FIGS. 5, 6, and 7 are waveform diagrams of signals V1 and V2 at each arousal level, and FIG. 8 is a cross-correlation signal value [)m at each arousal level. Characteristic diagram showing changes in , No. 9
The figure is a schematic cross-sectional side view showing a second embodiment of the dozing detection/prevention device of the present invention, and FIG. 10 is a block diagram of the second embodiment. 1.2... Permanent magnet 3... Glass-shaped support frame 4.5... Magnetic sensor 6... Signal processing discrimination device (discrimination means) 7... Alarm device (alarm means) Fig. 3

Claims (2)

[Claims] (1) A permanent magnet is interlocked with the eyelid, a magnetic sensor is attached to the spectacle-shaped support frame so as to face the eyelid, and the magnetic sensor detects changes in the magnetic field from the permanent magnet to detect movement of the eyelid. An eye movement detection method characterized by: (2) a permanent magnet in contact with the eyelids, a magnetic sensor disposed on the spectacle-shaped support frame, and a determining means for determining the arousal level of the subject from the movement state of the eyelids detected by the output signal of the magnetic sensor; A dozing detection/prevention device comprising: an alarm means for warning a subject when a decrease in arousal level is detected;