Sleep Inhibiting Alarm

Abstract

A method and device for detecting eye closure of an individual is provided comprising a signal source for directing signals at an individual's eye and means for detecting the said signals after reflection by the eye. An alarm system responsive to a chosen reflected signal level is also provided to alert the individual to the occurrence of an eye closed condition.

Description

This invention relates to a method and apparatus for controlling an electric device by eyelid movement and more particularly to a method and device which indicates eye closure.

The present invention is primarily a safety device to be used to arouse a vehicle operator who is becoming drowsy at the controls of his vehicle. In 1969, according to the National Safety Council, out of 60,000 traffic fatalities, 15,000 of them were directly attributable to drivers becoming drowsy and/or falling asleep at the wheel. With this fact in mind, the need for an effective safety device to eliminate this problem is obvious. Heretofore no device has been able to accomplish this purpose. Such a device would of necessity have to be not only completely harmless to the driver, but also be non-distracting to allow uninterrupted vehicle operation. Several attempts at devising such a device have been made, each ending in failure due to one reason or another. Until the invention herein described, no safe, effective and convenient method of arousing a sleepy driver has been developed.

In accordance with the present invention, apparatus is provided for generating and transmitting a signal onto the surface of an individual's eye, along with a signal detector positioned to receive the reflected signal. There have been a number of attempts to construct operational devices. However, devices of the type encompassed by this invention have attempted to operate on the theory that there is no reflection from the eyelid (U.S. Pat. No. Re. 24,197) or an assumed difference in reflection intensities between the pupil and the white portion of the eye. Most prior art devices tend not to work properly, as in U.S. Pat. No. Re. 24,197 or tend to accidental activation due to minor movements of the eye. It has been discovered that there is a significant variation in reflection intensity between the eyelid and eyeball, and that this difference can be effectively utilized to provide a device which is not subject to accidental activation due to minor eye movement. For instance, when the eye is open, most of the signal will be absorbed by the eyeball, only a small portion being reflected. When the eye is closed, a greater portion of the signal is reflected by the eyelid as compared to the eyeball.

The signal can be in any detectable form. However, there are certain medical, toxicological or oculogical limitations in signal form. For instance, the signal cannot be damaging to the eye, nor should it be annoying or distracting in any way. In addition, it should be of a character which will minimize accidental activation of the detector due to spurious signals. One way this can be achieved is by making the detector, the sensing circuitry, or both, responsive only to a selected signal band width. Of course the signal source will generate signals within the detectable band width. In order to further minimize these difficulties, two types of sources prove most effective: electromagnetic or sonic waves. Electromagnetic waves of certain frequencies, either non-polarized light in the upper reaches of the visible spectrum, infrared polarized light, or near-infrared frequencies have proven acceptable. Of course sonic waves at frequencies and intensities harmless to tissue, preferably outside the audible range, may also be used if desired.

An alarm is connected to the sensor circuitry adapted to respond to a selected signal level to indicate when the eye is closed. A timer or delay may be incorporated into the sensor circuitry which will permit an indicator, such as an alarm, to be activated when the eyelid has been closed for a preselected length of time.

The source and detector of the instant invention can be placed anywhere which will permit adequate detection and will not obstruct the eyes. A most practical position is on a pair of eyeglass frames, with or without prescription lenses, to be worn by the user.

In its preferred form, the apparatus of the invention includes a power source for energizing the signal source. The signal source has means for adjusting the frequency and the pulse width of the signal. When the apparatus is to be used by a vehicle operator, this component is contained either permanently in the vehicle or is portable. The power source may be a battery, either that of the vehicle or an internal battery pack may be provided, if desired. A convenient means of accomplishing connection with the vehicle battery in the portable form of the apparatus is to utilize the cigarette lighter socket. Alternatively, the entire signal source may be built into the dashboard of the car with a permanent battery connection.

The detection arrangement can be set up to monitor either a single eye of the individual, or both eyes simultaneously. Monitoring both eyes simultaneously is preferable for more accurate detection.

The device has many uses which will be apparent to one skilled in the art. Although the description is primarily directed to alerting a drowsing vehicle operator, it is understood that many other uses exist, such as electrically monitoring hospitalized patients who require close surveillance.

The drawings herein depict a preferred embodiment, wherein like numerals refer to like parts.

FIG. 1 is a block diagram functionally showing the parts of a preferred form of the apparatus and their relationship;

FIG. 2 is a circuit diagram of a pulse generator, used in the system of FIG. 1;

FIG. 3 is a circuit diagram of the power amplifier for the light source used in the system of FIG. 1;

FIG. 4 is a circuit diagram of the detector, power amplifier for an alarm, a timer and the alarm, also used in the system shown in FIG. 1; and

FIG. 5 is an isometric view of an eyeglass frame with source and detector.

As shown in the block diagram of FIG. 1, pulse generator 10 is connected with power amplifier 12 which, in turn, is connected to signal source 15. Signal source 15 directs a signal to the eye surface of an individual. A detector 16 is placed to intercept the signal as shown in FIG. 5. The output of the detector 16 is proportional to the received intensity, and this output is fed into a power amplifier 18. Power amplifier 18 amplifies the signal which is then fed to a timer 20. An alarm 22 is connected to the output of timer 20 and is activated only when an output from the timer occurs. Timer 20 is included in the circuit to provide means for discrimination between a blink and longer duration eye closure conditions. The timer is activated by the initial input from power amplifier 18, but will not pass the signal on to alarm 22 until a selected time interval has elapsed. In this manner, normal blinking will not activate the alarm.

The entire system is energized by a battery 24, each component being connected across it positive and negative terminals. Battery 24 can be either a vehicle battery or a portable battery pack. Alarm 22 can be any type conventionally known but is preferably audible. Each component mentioned above will be more fully described hereinafter.

FIG. 2 is a circuit diagram of pulse generator 10. Capacitor C.sub.1 (6.8 mfd) is normally charging at a rate determined by the combined resistance of resistor R.sub.3 (100 K) and variable resistor R.sub.2 (7.5 K) which are placed in series. When capacitor C.sub.1 has charged to a sufficient potential, a unijunction transistor Q.sub.1 , such as General Electric 2N1671, becomes operable and discharges the capacitor C.sub.1. Resistor R.sub.1 is used to load the transistor Q.sub.1 circuit to permit capacitor C.sub.1 to discharge through transistor Q.sub.1. Therefore, this portion of the circuit determines the R-C time constant according to adjustment of R, thus setting the frequency of the output pulse in the range from 100 KHz to 1 MHz.

Transistor Q.sub.2 (such as Motorola 2N334) and Q.sub.3 (such as Motorola 2N4409 or 2N4410) are biased into operation when the voltage at the emitter of Q.sub.1 is greater than the voltage at the emitter of Q.sub.3. This biasing takes place by means of diode D.sub.1, such as Fairchild FDH600, and resistor R.sub.4 (1 MEG). Resistors R.sub.5 (6.5 K) and R.sub.6 (12 K) perform the double function of biasing Q.sub.2 and limiting the current through transistor Q.sub.3. Transistor Q.sub.3 is connected to a capacitor C.sub.2 (200 mfd) which is in parallel with variable resistor R.sub.9 (5 K). By adjusting the resistance of R.sub.9, the discharging time of C.sub.2 is varied. The emitter of Q.sub.3 is connected to this parallel circuit through resistor R.sub.8 (3.7 K). Thus C.sub.1, R.sub.8 and R.sub.9 establish the on-off time of transistors Q.sub.2 and Q.sub.3 and establish the pulse width of the output signal of the generator.

The output of transistor Q.sub.1 is in saw-tooth wave form and is compensated by the feedback current from the output of the collector of transistor Q.sub.2 through diode D.sub.2 (such as Fairchild FDH600) and resistor R.sub.7 (1 MEG) to the emitter of transistor Q.sub. 1. This is done in order to prevent the setting of resistor R.sub.9 which controls the discharging time of C.sub.2 from effecting the charging time of C.sub.1 and thus changing the frequency. The feedback from transistor Q.sub.2 is equal to the current fed into the base of transistor Q.sub.3 at the switching point. These circuits can be utilized to vary the pulse width over a wide range while having no effect upon the frequency of the output signal.

Diode D.sub.3 (such as Fairchild FDH600) is provided to prevent any current flow from the emitter of Q.sub.2 to the positive pole of the battery.

Diode D.sub.1 (such as Fairchild FDH600) prevents any negative current flow through transistor Q.sub.3, which because of the sawtooth cycle draws current through resistor R.sub.4 thus driving the base of transistor Q.sub.3 positive. Capacitor C.sub.3 (200 mfd) is provided to prevent any extraneous pulses from affecting the power supply. Resistor R.sub.10 (4.3 K) is a load resistor which functions to establish a positive going pulse and diode D.sub.3 (such as Fairchild FDH600) is utilized to block any negative return into the positive battery lead.

This variable pulse generator is utilized to generate a pulse of the desired frequency and pulse width to the power amplifier 12 which in turn energizes the signal source 15, which in this case is light source 14. The correct adjustment of this generator will enable the light source to emit light of sufficient intensity and at a frequency which is non-distracting to the vehicle operator. At the same time, the pulse width of the light source output can be controlled to minimize the probability of accidentally activating the detector 16. Detector 16, of course, will be selected to be responsive to the incident light frequency and preferably only to light of the particular frequency emitted.

The battery is shown as 9 volts in FIG. 2. It is to be understood that a normal 12 volt automobile battery has a minimum output voltage of 9 v. Appropriate voltage control may be provided by voltage regulation if necessary. Alternatively, any source level may be used provided circuit components are adjusted accordingly.

FIG. 3 shows a circuit diagram of the power amplifier used to energize the light source 14. Power is provided from the same parallel circuit from the battery which energizes the pulse generator. Transistor Q.sub.4 (such as Motorola M901) is used to drive light source 14. Resistor R.sub.11 (5 K) is connected to diode D.sub.4 in the pulse generator 10. The voltage drop across resistor R.sub.11, when a negative going pulse is received, is sufficient to bias transistor Q.sub.4 into conduction. Resistor R.sub.12 (10 ohms) is provided to limit the current load across transistor Q.sub.4 when it is conducting.

FIG. 4 shows a circuit diagram of the detector, power amplifier, timer and alarm. This circuit is also connected in parallel with the power source. A detector 16, in this case a photo cell 17, is used to sense reflected light of a selected frequency. Transistor Q.sub.6 (such as Motorola QN4409) and transistor Q.sub.7 (such as Motorola 2N3055) are utilized in series with photo cell 17 to amplify the detected signal. Variable resistor R.sub.13 (5 K) is utilized to properly bias transistor Q.sub.7. Alarm 22 is disposed between transistor Q.sub.7 and the negative lead from the battery so as to be energized when necessary.

The pulse generator is adjusted so that the light transmitted from the light source has sufficient intensity to reflect a selected quantity off an eyelid. The frequency may be chosen to give maximum reflection by the eyelid to increase the difference in reflection intensity between the eyelid and the eyeball.

Small frequency adjustments may be made for each individual by simply operating the apparatus in the eye closed position. However, high frequencies, generally toward the end of the visible spectrum, can be used.

The instant apparatus turns off the light source when a positive going pulse is received at the base of transistor Q.sub.4 from pulse generator 10. Should the pulse generator fail to operate, transistor Q.sub.4 is normally biased "on" from resistor R.sub.10 which will allow constant light emittance at a brighter than normal intensity, as a safety feature.

The frequency output of pulse generator 10 has been described above. Preferably, the frequency chosen is considerably less than the time it takes to complete one blink. Under normal circumstances, the frequency output of the pulse generator should be at least 4 cps. and preferably, greater than 8 cps.

The reason for utilizing cyclic on-off times for the light source can be understood by reference to the alarm 22 and its associated timer 20. Timer 20 consists of a capacitor C.sub.4 which must reach a selected charge level before alarm 22 becomes operative. Each successive negative going pulse from pulse generator 10 adds to the voltage buildup across capacitor C.sub.4. A resistor, if necessary, can be provided in series with capacitor C.sub.4 which together form an RC circuit having a time constant directly proportional to the circuit values of these two parameters. To build up sufficient charge on capacitor c.sub.4 to operate the alarm, the negative going pulses must occur with sufficient regularity. In addition, the eyelid must be closed for the detector to receive a sufficient reflected signal intensity during this time interval so that the current to capacitor C.sub.4 generates a sufficient voltage drop across the capacitor to add to whatever voltage level is already present. The R of the alarm will bleed off charges from extraneous blinks.

It can readily be appreciated that by setting the pulse generator frequency and the time constant of the timer 20 at a selected level, the voltage pulses to capacitor C.sub.4 will occur with a frequency sufficient to build up a charge to operate alarm 22 when the eyelid is closed. As an example, if the eyelid is closed for a time duration longer than a normal blink, and the pulse generator generates a positive going pulse ten times a second, and if the RC time constant is equal to this time duration, a sufficient charge will be built up on the capacitor to cause alarm 22 to operate. Of course, the above assumes that the output of detector 16 will be sufficient to bias transistor Q.sub.6 and Q.sub.7 into a sufficiently conductive state to achieve a full charge. If the output of detector 16 is too low, little or no buildup of charge on capacitor C.sub.4 will occur since an insufficient biasing voltage will be applied to transistors Q.sub.6 and Q.sub.7.

FIG. 5 depicts the preferred arrangement of the signal source and detector on an eyeglass frame 32. A remote light source 14 is provided to radiate light energy into a bundle of optical fibers 30. The bundle 30 is split such that it has ends at each corner of the eyeglass frame 32. Light is thus transmitted to the surface of the individual's eyes. Fiber optics are utilized to prevent the individual from being annoyed by the heat generated by the light source. In addition no lens is necessary as the light is columnized by the use of the fiber optic bundle for easier detection. Detectors 16, 16 are placed at the bottom of the frames adjacent to the end of the fiber optics bundle 30. The detectors are electronically connected by means of wires 34,34 to the power amplifier 18. In operation, when the eyelid is closed, the light from light source 14 conducted through fiber optics bundle 30 will be reflected from the individual's eyelids and sensed by detectors 16,16. The detectors will then emit an electrical signal conducted by means of wires 34,34 to power amplifier 18, which will in turn, if the duration of the signal from the detector is longer than a predetermined time interval, activate the alarm.

It is to be understood that modifications may be made which are not specifically described herein but which will be readily apparent to those skilled in the art. It is intended to cover all such modifications which fall within the spirit and scope of the invention as defined by the appended claims.

Claims

1. An apparatus for detecting eye closure of an individual comprising:

a signal source for generating and transmitting a signal into the individual's eye;

a power source for energizing said signal source;

means for detecting the difference in reflected signal intensity between the signal reflected by the opened eye of the individual and the higher signal intensity reflected by the eyelid of the individual when the eye is closed, comprising a photosensitive signal generator;

said signal source comprising a pulse generator to generate a signal; an amplifier to amplify said signal and a light energized by said signal;

said pulse generator comprising means for generating a sawtooth pulse at a desired frequency;

means for varying the width of the generated pulse and means for compensating said generating means so as to eliminate the dependency of frequency upon said pulse width varying means;

said generating means comprising a unijunction transistor and a capacitor, said capacitor being connected between the emitter of said transistor and the negative lead of said power source such that upon charging to the activation voltage of said transistor said transistor is activated to discharge said capacitor, and means for varying the charging time of said capacitor;

2. The apparatus according to claim 1 wherein said pulse width varying means comprises;

a second transistor biased by said capacitor to operate when the bias voltage is less than the voltage at the emitter of said second capacitor,

means for adjusting the voltage at the emitter of said second transistor, and

a third transistor biased by said second transistor to operate whenever said second transistor is operable such that the signal output at the collector of said third transistor has a pulse width dependent upon said

3. The apparatus according to claim 2 wherein said adjusting means comprises a second capacitor and a variable resistor in parallel with said

4. The apparatus according to claim 2 wherein said compensating means comprises:

a feedback circuit for connecting the collector of said third transistor to the first capacitor such that the charging time of said first capacitor is

5. The apparatus in accordance with claim 2 wherein the input of said amplifier is connected to the collector of said third transistor and

6. The method of detecting eye closure of an individual comprising:

energizing a light to emit a light ray pulse of a particular frequency and pulse width, amplifying said pulse and energizing said light with the signal output from said amplifier converting a constant direct current into a pulsed signal of designated frequency and varying the width of said pulse without changing the frequency of said signal;

directing said light to the individual's eye;

detecting the reflected signal from the eye in both the open and closed position of the eye, and providing an alarm responsive to the signal reflected when said eye is in said closed position;

the step of converting a constant direct current comprises the steps of charging a capacitor, biasing a transistor to operate when the capacitor is fully charged to discharge said capacitor, adjusting resistance to vary the charging time of said capacitor and biasing a second transistor to

7. The method in accordance with claim 6 wherein the step of varying the pulse width comprises:

charging a second capacitor when said second transistor is operational,

varying the discharging time of said second capacitor by means of an adjustable resistor,

controlling the emitter voltage on a third transistor in accordance with the discharging time of said second capacitor such that the output pulse at the collector of said third transistor has the frequency determined by the charging time of said first capacitor and a pulse width determined by

8. The method according to claim 7 wherein the step of varying the pulse width further comprising compensating the bias of said second transistor to keep the charging time of said first capacitor independent of the discharging time of said second capacitor.