GB2133598A - Apparatus for producing an alarm in response to the sensed dozing of a subject - Google Patents

Abstract

Safety apparatus for sensing when a person is beginning to doze and for providing an alarm indication for preventing dozing in response to sensed closure of the person's eyelids. A train of optical pulses is directed to and reflected from the eye, such that sensing of the train of reflected pulses indicates closure of the eye. Signal processing circuitry is provided to prevent false alarms due to blinking and background changes. The apparatus may be embodied readily in ordinary eyeglasses. <IMAGE>

Description

SPECIFICATION Apparatus for producing an alarm in response to the sensed dozing of a subject The present invention relates to safety devices generally and more particularly to devices for producing an alarm in response to the sensed dozing of an individual.

Background of the invention The need for reliable sensing of the imminent dozing of a person and the prevention thereof has long been realized. The most widespread potential application of techniques for this purpose is to drivers of motor vehicles, many hundreds, if not thousands, of whom are kiiled and maimed annually asthe resultof falling asleep atthe wheel. Other applications include operators of machinery, guards and individuals in other situations wherein a dangerous or damaging occurance could result from dozing of the individual.

There has been proposed apparatus for providing an alarm indication of the dozing of a subject which employs a brain wave sensor for indicating the existence of a pattern of brain waves which is characteristic of dozing. Such apparatus is relatively complex and expensive and is not considered to be suitable for widespread use, such as by drivers of automobiles.

Summary of the invention The present invention seeks to overcome the limitations and the disadvantages of the prior art apparatus and to provide apparatus for providing a preventative alarm indication ofthe imminent dozing of a subject which operates on the basis of eyelid closure.

There is thus provided in accordance with an embodiment of the present invention apparatus for providing a preventative alarm indication of the imminent dozing of a subject comprising apparatus for transmitting electromagnetic radiation to the eye of a subject, apparatus for sensing the reflection of the transmitted electromagnetic radiation from the eye of the subject, whereby the open or closed state of the eyelid of the eye of the subject modulates the radiation received by the sensing apparatus, and alarm apparatus responsive to the output of the sensing apparatus for producing a dozing prevention alarm to the subject in response to sensed imminent dozing of the subject.

Further in accordance with an embodiment of the invention, the transmitting apparatus comprises apparatus for transmitting a train of pulses in the infrared range.

Additionally in accordance with an embodiment of the present invention, the sensing apparatus includes a frequency filterfor filtering out radiation inputs out- side of the range of the reflected train of pulses.

Further in accordance with a preferred embodiment of the invention, the sensing apparatus comprises comparator apparatus which compares the received train of pulses with a variable threshold, thereby to remove background effects.

Additionally in accordance with an embodiment of the present invention,the sensing apparatus also comprises time scale filtering logic circuitry which is operative to filter out short time scale variations in the received train of pulses which could result from blinking or similar activities which do not indicate imminent dozing.

Brief description of the drawings The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: Figure 1 is a pictorial illustration of eyeglasses including the dozing preventative apparatus of the present invention; sensing and preventing dozing constructed and operative in accordance with a preferred embodiment of the present invention; and Figures 3A-3F are detailed schematic illustrations of the apparatus of figure 2.

Detailed description of the preferred embodiment Reference is now madeto Figure 1 which illustrates apparatus ofthe present invention embodied in a pair of ordinary eyeglasses. It may be seen readily that a pulse transmitter 10, typically in the form of an LED, and a pulse receiver 12, typically a phototransistor, are located adjacentthe bottom portion 1 4 of the iens carrying frame 16 of the eyeglasses. Electronic circuitry 18 and an alarm device 20, such as a miniature buzzer, are preferably located in an enclosure 22 mounted on one of the arms of the eyeglasses or integrally formed therewith. It is noted that the transmitter 10 and the receiver 12 are disposed in optical communication with the eye of a wearer for determining whether the eye is open or closed.The output of receiver 12 is supplied to circuitry 18 by conductors which are not shown in this drawing.

Similarly transmitter 10 is connected to a power source and to control circuitry embodied in circuitry 18 by means of conductors which are not illustrated.

It is appreciated that the eyeglasses of Figure 1 may be worn and used substantially identically to ordinary eyeglasses in addition to their protective feature.

Reference is now made to Figure 2 which is a block diagram illustration of apparatus for sensing and preventing dozing constructed and operative in accordance with a preferred embodimentofthe present invention. The apparatus comprises a transmitter 30, typically a Gallium Arsenic Light Emitting Diode which provides radiation at a wavelength of about 0.9 microns, in the infrared range. A preferred wavelength of 0.93 microns.

As noted above, the transmitter 30 is directed at the cornea of the human eye so as to provide reflection and scattering of the emitted radiation from the transmitter 30 from the eye. It is appreciated that the reflection and scattering is modulated by the open or closed state of the eye. Radiation reflected from the human eye is received by a receiver 32, such as a silicon phototransistor, via a filter 34 which is operative to absorb radiation of wavelength less than 0.9 microns, thereby to remove the effects of background radiation. To save power, the receiver may be operated only during times in the vicinity of transmissions. Coordinatin of the operation of the transmitter 30 and ofthe receiver 32 is provided by timing signals received from timing and logic circuitry 50 described hereinbelow.

The output from receiver 32 is supplied to a preamplifier 36, typically having a gain of 20, and thence to frequency filter 38. It is noted that transmitter 30 normallytransmits a series of bursts of 8 pulses each, the pulses of each burst having a frequency of 50 KHz, and the bursts having a frequency of 14 Hz. Filter 38 is an active filter and is operative to pass only the 50 KHz pulses and to block DC and other spurious signals and biases.

The output of filter 38 is supplied to an Automatic Gain Control loop comprising an amplifier 40 which receives the input from filter 38 at a first inputthereof.

The amplifiertypically has a gain of between 2 and 20.

The output of amplifier 40 is supplied to a time averager 42. The time averager 42 is operative to provide a variable background threshold by integration of the received pulses. An output of the time averager 42 is supplied to a feedback amplifier 44 whose output is supplied to a second input of amplifier 40. The output of time averager 42 is also supplied to a comparator 46, which may operate similar to a flip flop. Comparator 46 is operative to change state in response to a change in the intensity of the pulses received by typically 20%. The output of comparator 46 is supplied to an alarm device 48, such as a buzzer.

The Automatic Gain Control loop is operative to stabilize the voltage appearing at its output. The amplified pulses from amplifier 40 are rectified synchronously with the transmitted pulses and integrated by time averager42. The output voltage oftime averager 42 is operative to control the gain of amplifier 40 via feedback amplifier 44. The time constant of the Automatic Gain Control loop is relatively long (about 30 seconds) so that relatively quick changes can pass therethrough and trigger the comparator 46. Optionally, the AGC loop may be fastened by the use of a reset button associated with the feedback amplifier 44.

Comparator 46 is normally in a low state (0). The receipt of a burst of high amplitude pulses of overall amplitude greater than 5 volts by at least 20% causes the comparator to change its position to a high state (1). The increase in the amplitude of the pulses indicates a closing of the eyelid. The closing of the eyelid provides received radiation of greater amplitude at the receiver32 due to a numberof reasons, including greater propinquity of the reflecting surface and a difference in the nature of the radiation scattering produced by the eyelid as opposed to the cornea.

The change of state of comparator 46 allows an up/down counter to run. If four such bursts are detected consecutively, an alarm indication is provided. The occurance of four such bursts indicates thatthe subject has closed his eyes in a dozing mode.

The alarm indication may continue until the subject again opens his eyes. When the subject opens his eyes and the pulses decrease in amplitude, the comparator 46 returns to its low state.

Timing and logic circuitry 50 provides timing outputs to transmitter 30, receiver 32, frequency filter 38, time averager 42, feedback amplifier 44 and alarm device 48 to ensure coherent operation thereof.

The timing circuitry is based on an oscillator which operates at 50 KHz. The oscillator output is fed to a 12 bit binary counter, whose output determines the periodicity of transmission of transmitter 30 and of reception by receiver 32.

Reference is now made to Figures 3A-3F which a schematic illustration ofthe apparatus of Figure 2. For convenience each portion ofthe circuitry illustrated in Figure 3 is identified by a reference numeral which corresponds to the designation of such circuitry in the block diagram illustration of Figure 2.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove.

Rather the scope of the present invention is defined only by the claims which follow:

Claims (7)

1. Apparatus for providing a preventative alarm indication of the imminent dozing of a subject comprising: means for transmitting electromagnetic radiation to the eye of a subject; means for sensing the reflection of the transmitted electromagnetic radiation from the eye ofthe subject, whereby the open or closed state of the eyelid of the subject modulatesthe radiation received by the sensing means; and alarm means responsive to the output of said sensing means for producing a dozing prevention alarm to the subject in response to variations in the sensed reflection of the transmitted electromagnetic radiation from the eye of the subject.

2. Apparatus according to claim 1 and wherein said transmitting means comprises means for transmitting a train of pulses.

3. Apparatus according to claim 2 and wherein said train of pulses is in the infrared range.

4. Apparatus according to claim 1 and wherein said sensing means comprises a frequency filter for filtering out radiation inputs outside of the frequency range ofthe electromagnetic radiation transmitted by said transmitting means.

5. Apparatus according to claim 1 and wherein said sensing means comprises comparator means which compares the received train of pulses with a variable threshold, thereby to remove background effects.

6. Apparatus according to claim 5 and wherein said sensing means comprises automatic gain control means for providing said variable threshold.

7. Apparatus according to claim 1 and wherein said sensing means comprises time scale filtering means for filtering out short time scale variations in the electromagnetic radiation received by the sensing means which could result from blinking or similar occurances which do not indicate imminent dozing.