APPARATUS FOR MONITORING THE EYES OF AN OPERATOR

Abstract: Apparatus for monitoring the eye of a subject comprising: apparatus (10, 12) for directing infra-red radiation at the eyes of a subject; apparatus (22, 24) for sensing infra-red radiation retro-reflected by the retina through the cornea of the subject; and apparatus (28) for providing a sensible output indication in the absence of expected received retro-reflected radiation, indicating the closing of the subject's eyes or direction of his eyes outside of a desired angular region.

Description: FIELD OF THE INVENTION The present invention relates to electro-optical alertness monitoring apparatus and more particularly to apparatus for monitoring the eyes of an operator. BACKGROUND OF THE INVENTION Various types of apparatus have been proposed for maintaining alertness of drivers and operators of machinery. U.S. Patent 2724109 describes a sleep inhibitor for automobile drivers wherein light from a lamp is reflected from the driver's eyeball in order to activate an alarm when the eyeball is covered by the eyelid for more than a predetermined time. U.S. Patent 3379885 to Nork describes a sight switch employing an infrared source and sensor which distinguishes between reflections from the white of the eyeball and the iris. Two other U.S. Patents Nos. 4397531 and 4625337, use relatively expensive two dimensional image scanners and very heavy software to analyze the image. U. S. Patent No. 4397531 does disclose electro-optical alertness monitoring apparatus which has means for directing radiation at the eyes of the subject and a video camera for sensing radiation retroreflective by the retina through the cornea of an eye of a subject. The present invention seeks to provide improved apparatus for monitoring operator alertness. In accordance with the present invention, there is provided apparatus for monitoring one of the eyes of a subject comprising: means for directing radiation at the eye of a subject; and sensing means for sensing radiation retroreflected by the retina through the cornea of the eye; characterised by scanning means for causing said means for directing radiation and said sensing means to scan a given angular sector in at least one direction; and output means triggered by the sensing means for providing an output indication in the absence of expected received retroreflected radiation. 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: Fig. 1 is a partially pictorial-partially block diagram illustration of apparatus for monitoring alertness constructed and operative in accordance with a preferred embodiment of the present invention; and Fig. 2 is a partially schematic, partially block diagram, illustration of electronic circuitry useful in the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is now made to Fig. 1, which illustrates a preferred embodiment of the present invention including scanning platform 2 which is typically mounted and driven by means of a motor 4 for scanning rotation in a horizontal plane with respect to a reference mounting surface, such as the dashboard of a vehicle. A radiation source 10, is mounted onto platform 2, typically comprises a laser diode or an infrared emitting diode and emits radiation via a collimating lens 12, such as a cylindrical lens, so as to define a fan 14 of radiation disposed typically in a vertical plane. The radiation output via collimating cylindrical lens 12 typically passes through a beam splitter 16 of conventional construction, which is operative to transmit a part of the beam through an IR filter 18, and to reflect the remainder. Most of the light transmitted in fan 14 via filter 18 is reflected in a diffuse manner from the various surroundings. Light, within a given range of angles, impinging on the retina through the cornea of an operator's eye is retroreflected back in the direction from which it impinged on the cornea. Retroreflected light received via the cornea impinges on beam splitter 16 via filter 18 and is reflected by beam splitter 16, via a mirror 20 and a cylindrical or convex lens 22 to an infra-red detector 24, such as a photovoltaic silicon PN detector. It is appreciated that all of the apparatus described above is mounted onto scanning platform 2. Radiation source 10 receives electrical power from emitter electronic circuitry 26, which is illustrated in Fig. 2, causing source 10 to transmit IR pulses at high frequency or in a continuous wave form. When the operator's eye is directed within a suitable range of directions with respect to the radiation source, a retroreflected IR pulse train or continuous wave, as the case may be, is received by detector 24 and transmitted to detector electronic circuitry 28, which is illustrated in Fig. 2. This circuitry receives timing inputs from emitter electronic circuitry 26 and senses when anticipated retroreflected signals are not received within a predetermined time range. The absence of such retroreflected signals may indicate that the operator has closed his eyes, or looked outside of a predetermined permitted viewing range. When appropriate, circuitry 28 produces an alarm indication to a warning device 30, such as an audio alarm. Operation of the warning device 30 may be terminated when the retroreflected light is once again received by detector 24. Reference is now made to Fig. 2 which illustrates electronic circuitry employed in the apparatus of Fig. 1. An oscillator 40, typically operating at 10KHz, provides an output to a power transistor 42, which provides a desired pulse output to a laser diode 44, which serves as radiation source 10 (Fig. 1). The output of oscillator 40 is also provided via a flip flop circuit 46 to the base of a transistor 48, which receives the output of IR detector 24 (Fig. 1) via an operational amplifier 50. Transistor 48 thus acts as a switch, permitting the output from operational amplifier 50 to pass only when it is received within a predetermined coincidence time of the transmission of an IR pulse by laser diode 44, thereby to prevent false detection due to spurious IR sources. The output from transistor 48 is supplied via an operational amplifier 52 to a comparator 54, which compares it with a predetermined reference and provides a RESET input to a counter 60 and to a DFF circuit 64. A free oscillator 58, typically operating at 30 Hz provides a clocking input to counter 60. The RESET input is provided by comparator 54 when retroreflected radiation is sensed by detector 24. Should counter 60 count up to a predetermined threshold count without being reset in response to detection of retroreflected radiation, such count output causes state logic circuitry 62, which receives counter outputs, to activate an alarm 66, such as an audio alarm, via the DFF circuitry 64. DFF circuitry 64 is operative to terminate the operation of alarm 66, when it receives the RESET signal, indicative of sensed retroreflected radiation. 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: Apparatus for monitoring one of the eyes of a subject comprising; means (10, 12, 16, 18) for directing radiation at the eye of a subject; and sensing means (24) for sensing radiation retroreflected by the retina through the cornea of the eye; characterised by scanning means (2, 4) for causing said means (10, 12, 16, 18) for directing radiation and said sensing means (24) to scan a given angular sector in at least one direction; and output means (28, 30) triggered by the sensing means for providing output indication in the absence of expected received retroreflected radiation. Apparatus according to claim 1 and wherein said radiation is outside the visible spectrum. Apparatus according to claim 1 or 2 and wherein said radiation is infrared radiation. Apparatus according to any of the preceding claims and wherein said scanning means are operative to scan in two orthogonal directions. Apparatus according to any of the preceding claims and wherein said scanning means are operative to scan in a horizontal plane. Apparatus according to any of claims 1 to 5 and wherein said means for directing comprise a collimating lens. Apparatus according to any of claims 1 to 6 and wherein said sensing means comprise a beam splitter (20) and an infrared detector (24). Apparatus according to any of claims 1 to 7 and wherein said output means include circuitry (28) receiving inputs representing the timing of radiation outputs from said means for directing radiation and inputs representing the timing of retroreflected radiation received by said sensing means for providing an alarm actuation output signal. Apparatus according to any of claims 1 to 8 and wherein said output means for providing an output indication in the absence of expected received retroreflected radiation is operative for indicating the closing of the subject's eyes or direction of his eyes outside of a desired angular region.

Inventors: GERLITZ, YONATAN, MORAN, DAN
Applicants: RASAAT
Application year: 1988
Main classification: A61B3
IPC codes: B60K28, A61B3, A61B5, B60W30