Abstract:
In a preferred embodiment, an infrared optical position detection system, including: an infrared emitter to emit infrared radiation toward an object; a receiver to receive the infrared radiation scattered by the object and to determine position of the object; the receiver including a detector; and the receiver including an optical system having two and no more than two lenses.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to optical position sensor systems generally and, more particularly, but not by way of limitation, to a novel infrared optical position sensor system which may be employed to determine the position of an occupant of a vehicle and to disable an air bag restraint if it is determined that the occupant may be injured by deployment of the air bag restraint. 
     2. Background Art 
     While the present invention is described, for illustrative purposes, as being applied to occupant classification and position detection in a vehicle, it will be understood that it can be employed in any optical receiver system in which optical image quality is not important. 
     Inflatable restraints, or air bags, are increasingly being used in vehicles to protect an occupant of a vehicle in case an accident occurs. Typically, a control system senses the occurrence of an accident and causes the air bag to deploy to protect the occupant from colliding with the windshield or dashboard, for example, of the vehicle. An occupant proximity sensor system may comprise part of the control system. Such a system monitors the position of the occupant of the front-outboard passenger seat and automatically, without any action required of the driver or the passenger, determines whether to suppress deployment or allow deployment of the front air bag (and perhaps the side air bag also, if the vehicle is so equipped) applicable to this position. The determination whether or not to suppress air bag deployment is made based on the occupant being in the “at-risk” zone or on classifying the occupant as being in a rear-facing infant seat (RFIS). Conversely, the system allows air bag deployment for a properly seated occupant, i.e., seated with hips back, rearward on the seat cushion and with back resting on the seat back, outside of the at-risk zone. 
     Upon determining the position/classification of the occupant of the front-outboard seat, the system sends a signal to the sensing and diagnostic module indicating whether to suppress or allow air bag deployment. The system also sends a signal to a display indicating whether the air bag is in a suppressed or an enabled state. If the air bag is in a suppressed state, the signal alerts the driver or passenger to take corrective action, if desirable. 
     There are many kinds of sensor systems under development. So far, there are mainly two kinds of occupant position sensors: infrared- and ultrasonic-based sensors. Compared to the ultrasonic sensor, the infrared sensor has the fastest response time. An infrared occupant position sensor can classify and recognize an occupant in less than 10 milliseconds. 
     The typical infrared occupant position sensor has two main elements: an emitter and a receiver. The emitter is a light source that radiates infrared light and illuminates target objects. The receiver consists of an optical system and a detector. The optical system collects light from the target objects and focuses the light signal on the detector. In most such applications, the scattering signal is very weak. 
     The common requirement for the receiver/optical system is to receive more light and ensure that the spot size on the detector is sufficiently small to allow the optical system to produce the required image quality. Unfortunately, in most cases the scattering light is very weak. In addition, the size of the detector is limited and a highly efficient use of detectors is required. An effective receiver optical system should have a large aperture, short focal length, and large field of view. Unfortunately, a major disadvantage of known such optical systems is complexity and a concomitant prohibitively high cost. 
     Accordingly, it is a principal object of the present invention to provide an infrared vehicle occupant position detection system for classifying and determining the position of a vehicle occupant that is highly accurate and reliable. 
     It is a further object of the present invention to provide such a vehicle occupant position detection system that is economical to construct. 
     It is an additional object of the present invention to provide such a vehicle occupant position detection system that has a large aperture, a short focal length, and a large field of view. 
     Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures. 
     SUMMARY OF THE INVENTION 
     The present invention achieves the above objects, among others, by providing, in a preferred embodiment, an infrared optical position detection system, comprising: an infrared emitter to emit infrared radiation toward an object; a receiver to receive said infrared radiation scattered by said object and to determine position of said object; said receiver including a detector; and said receiver including an optical system comprising two and no more than two lenses. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Understanding of the present invention and the various aspects thereof will be facilitated by reference to the accompanying drawing figures, provided for purposes of illustration only and not intended to define the scope of the invention, on which: 
     FIG. 1 is a cut-away, side elevational view of a vehicle, with an occupant seated therein, and with the position of the occupant being determined by the system of the present invention. 
     FIG. 2 is a cut-away, side elevational view of a vehicle, with a child seated in a rear facing infant seat, and indicating the consequences of having an air bag deployed in this situation. 
     FIG. 3 is a cut-away, side elevational view of a vehicle, with an occupant seated such that the occupant is partially within the at-risk zone. 
     FIG. 4 is a block logic flow diagram for the system of the present invention. 
     FIG. 5 is a side elevational view of the two lenses employed in the system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference should now be made to the drawing figures on which similar or identical elements are given consistent identifying numerals throughout the various figures thereof, and on which parenthetical references to figure numbers direct the reader to the view(s) on which the element(s) being described is (are) is best seen, although the element(s) may be seen on other figures also. 
     FIG. 1 illustrates a person  10  seated on the front-outboard seat  12  of a vehicle  14 . As shown, person  10  is properly seated on the seat  12 , with his hips and back placed against the back of the seat, and with the seat set at a safe distance spaced from dashboard  20  of vehicle  14 . Also illustrated on FIG. 1 is an alternative arrangement in which an infant  16  is seated in a rear facing infant seat  18 , clearly within the at-risk zone. 
     Mounted in a console  24  behind a rear view mirror  26  in vehicle  14  is an emitter module  30 , which emits infrared radiation, and a receiver module  32 , which receives infrared radiation scattered from objects in the front of the passenger compartment of the vehicle. The receiver also includes a position sensitive detector that detects the energy center of the light spot on the detector. 
     The recommended light spot size on the detector is larger than 200 micrometers and the present system produces a larger spot size. The image quality of the receiver is not important. The system recognizes occupant type, as well as occupant position and posture, with dynamic occupant position being determined using triangulation. 
     Modules  30  and  32  are connected to a control system (not shown) which classifies person  10  and determines if the person is out of the at-risk zone and is not seated in a rear facing infant seat. In this case, person  10  is safely seated and, accordingly, the control system will enable the air bag (not shown on FIG. 1) associated with the front-outboard seat, so that the air bag can be deployed in case an accident occurs. The control system will also provide an indication on a display  40  that the air bag is enabled. As noted above, if display  40  should indicate that the air bag is suppressed, then person  10  or the driver of vehicle  14  would have the opportunity to take corrective measures. 
     FIG. 2 illustrates the consequences of failure to disable an air bag when the air bag is used with a child seated in a rear facing infant seat. Here, a child  50  is seated in a rear facing infant seat  52  that is attached to the front-outboard seat  54  of a vehicle  56 . In this case, deployment of air bag  60  has not been suppressed and the air bag has deployed against rear facing infant seat  52 , forcing the rear facing infant seat rearward. It will be appreciated that such an action can cause serious injury or death to child  50  and, in fact, there have been reported instances of such injury or death. 
     FIG. 3 illustrates the potential consequences of a person disposed within the at-risk zone. Here, a person  70  is seated on a front-outboard seat  72  in a vehicle  74 . Person  70  is properly seated on seat  72 , with his hips and back against the back of the seat; however, in this case, the seat has been moved too far forward, thus placing part of the body of the person within at risk-zone  80 . Thus, in this case, deployment of an air bag, such as air bag  60  (FIG. 2) has the potential of causing serious injury or death to the person and again, in fact. there have been reported instances of such injury or death. Operation of a proper position sensing system (FIG. 1) will suppress deployment of the air bag and will alert person  70  and the driver of vehicle  74  to the potential hazard. In this case, person could simply move seat  72  rearwardly to place himself outside of at risk zone  80 , the position sensing system will enable the air bag, and display  40  (FIG. 1) would indicate enablement of the air bag. 
     FIG. 4 illustrates the control logic for the position sensing and control system of the present invention. Here, emitter element  30  (FIG. 1) transmits infrared radiation and the reflection thereof is received by receiver element  32  (FIG.  1 ). A sensing and diagnostic module  90  analyzes the scattered radiation and determines the status and position of an occupant of a front-outboard seat. If the occupant is in the at-risk zone (FIG. 3) or if the occupant is seated in a rear facing infant seat (FIG.  2 ), sensing and diagnostic module  90  will cause suppression of air bag deployment, at  92 . If the occupant is outside of the at-risk zone and is not seated in a rear facing infant seat, sensing and diagnostic module  90  allows enablement of the air bag at,  94 . In either case, the status of the air bag is displayed, at  96 . As noted above, the procedure described with reference to FIG. 4 takes less than  10  milliseconds. This procedure is continuously reiterated while the vehicle is in operation, so that changes in position can be immediately detected and the air bag disabled when appropriate. 
     FIG. 5 illustrates the lens portion of an optical system, constructed according to the present invention, and generally indicated by the reference no numeral  100 . Lens portion  100  consists of two lenses: an aspheric lens  110  used in combination with a symmetric-convex spherical lens  112 . The convex aspheric surface of aspheric lens  110  receives scattered infrared radiation (FIG.  1 ), while the spherical surface of aspheric lens  110  contacts spherical lens  112 , and the spherical lens faces the detector (not shown). 
     Most preferred parameters for aspheric lens  110  are: focal length, f a =12 mm, diameter of the lens, D a =18 mm, and back focal length, f ab =6.9 mm. Most preferred parameters for spherical lens  112  are: focal length, f s =12 mm, diameter of the lens, D s =15 mm, and back focal length, f sb =18.3 mm. Most preferred parameters for the receiver optical system are: effective focal length, f=8.7 mm, aperture diameter of the system, D=15.7 mm, and back focal length f b =3.77 mm. The field of view of the optical system is 50 degrees. While the foregoing parameters can be changed, depending on the requirements of focal length and aperture, these parameters provide the simplest and most economical system. The system can be employed in any receiver optical system in which the image quality of the system is not important. 
     In the embodiments of the present invention described above, it will be recognized that individual elements and/or features thereof are not necessarily limited to a particular embodiment but, where applicable, are interchangeable and can be used in any selected embodiment even though such may not be specifically shown. 
     Terms such as “upper”, “lower”, “inner”, “outer”, “inwardly”, “outwardly”, and the like, when used herein, refer to the positions of the respective elements shown on the accompanying drawing figures and the present invention is not necessarily limited to such positions. 
     It will thus be seen that the objects set forth above, among those elucidated in, or made apparent from, the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown on the accompanying drawing figures shall be interpreted as illustrative only and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.