Abstract:
An optical system for vehicle operating monitoring is disclosed. The optical system includes at least one illuminator that illuminates a profile of a vehicle operator and an imager in optical communication with a reflector that captures a reflected image of the vehicle operator profile from the reflector. A method is also disclosed.

Description:
FIELD OF THE INVENTION 
   The invention relates to vehicle operator safety systems and more particularly to an optical system for vehicle operator monitoring. 
   BACKGROUND OF THE INVENTION 
   Optical systems for vehicle operator monitoring have been used in various applications including, but not limited to, occupant detection and occupant security. The proposed design and integration of such conventional optical systems have included many performance and functionality issues, which impacts cost and complexity in the overall design of the passenger compartment area. 
   Referring to  FIGS. 10A-11 , conventional integration designs have located an imager  1  (i.e., a camera) of the optical system within the instrument cluster  2 , on the A-pillar, or in the center console. In such implementations, the imager  1  was located in a directly opposing relationship, relative to the driver, to directly capture images of the driver during the operation of the vehicle. However, in order to ensure the proper operation of such an optical system, the imager  1  must not be obstructed at any time. As seen in  FIG. 10B , by locating the imager  1  in the instrument cluster  2 , the imager  1  is susceptible to obstructions caused by the driver&#39;s hands, wrists, and arms when the driver moves his hands from the 2-o&#39;clock and 10-o&#39;clock positions ( FIG. 10A ) to a new position proximate the 12-o&#39;clock area ( FIG. 10B ) of the steering wheel  3 . Referring to  FIG. 11 , if the imager is located about a headliner area, the brim  4  of an operators&#39; hat  5  may obstruct a portion of the driver&#39;s face  6 . In yet another situation, if the imager is located in the A-pillar area, obstructions to the driver&#39;s face may be reduced, however, an A-pillar located imager is limited to capturing a partial profile of the driver&#39;s face due to the off-center location of the imager. 
   As such, a need exists for improving optical systems for vehicle operator monitoring. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The inventors of the present invention have recognized these and other problems associated with optical systems for vehicle operator monitoring. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1A  is an exploded, perspective view of an optical system according to an embodiment; 
       FIG. 1B  is an exploded, perspective view the optical system according to another embodiment; 
       FIG. 2A  is an exterior, environmental perspective view of the optical system according to an embodiment; 
       FIG. 2B  is an exterior, environmental perspective view of the optical system according to another embodiment; 
       FIG. 3  is a passenger compartment perspective view of the optical system according to an embodiment; 
       FIGS. 4A  is a top view of an imager and illuminator arrangement according to the embodiment shown in  FIG. 3 ; 
       FIGS. 4B-4D  are alternative embodiments of the imager and illuminator arrangement of  FIG. 4A ; 
       FIG. 5  is a partial cross-sectional view of the imager located about an instrument panel and a reflector positioned on an interior surface of a windshield according to an embodiment; 
       FIGS. 6A  illustrates a profile of a vehicle operator according to an embodiment; 
       FIG. 6B  illustrates another profile of a vehicle operator according to an embodiment; 
       FIG. 7  is a magnified view of the windshield and reflector illustrated in  FIG. 5  according to an embodiment; 
       FIG. 8  is a passenger compartment view illustrating a field of view of the optical system; 
       FIG. 9A  is a normalized CMOS imager response curve; 
       FIG. 9B  is a normalized response curve of an infrared light emitting diode; 
       FIG. 9C  is a normalized response curve of an infrared band-pass filter; 
       FIG. 10A  is first perspective view of a conventional optical system; 
       FIG. 10B  is a second perspective view of the conventional optical system of  FIG. 10A ; and 
       FIG. 11  is a perspective view of an image captured by a conventional optical system. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The above described disadvantages are overcome and a number of advantages are realized by an inventive optical system  10   a,    10   b  as shown generally in  FIGS. 1A and 1B . The optical system  10   a,    10   b  comprises at least one illuminator  12 , an imager  14 , and a mirror, which is hereinafter referred to as a reflector  16 . Preferably, the imager  14  is substantially located about the centerline the vehicle operator&#39;s profile, P. The reflector  16  is located about an inboard surface  18  of a windshield  20  and in optical communication with the imager  14 . If desired, a band-pass filter  22  may be positioned in front of the imager  14  to block ambient light and prevent saturation of the imager  14 . 
   As shown in  FIG. 1A , the illuminator  12  may be co-located with the imager  14 , or, alternatively, as shown in  FIG. 1B , the illuminator  12  may be remotely located with respect to the imager  14 . When the illuminator  12  is co-located with the imager  14 , light (i.e., dashed line L) from the illuminator  12  is reflected off of the reflector  16  toward the vehicle operator, O. When the illuminator  12  is remotely located from the imager  14 , light, L, from the illuminator  12  is projected directly to the vehicle operator, O, which is then reflected toward the reflector  16 . As a result, the imager  14  captures an image of the operator&#39;s profile, P, with reflected optics (i.e. dashed line R). Accordingly, the light, L, that is directed back to the imager  14  by the reflector  16  enables the optical system  10   a,    10   b  to provide an unobstructed operator profile, P. 
   Referring to  FIG. 2A , an imager  102  of an optical system  100  is located on top of a valance panel  104 . A lens  106  of the imager  102  directly faces a reflector  108  in such a manner as to capture an image of the operator&#39;s profile, P, with reflected optics as described above. According to another embodiment shown in  FIG. 2B , an imager  202  of an optical system  200  is located within a recessed bezel  204  of a valance panel  206 . As similarly described in  FIG. 2A  above, a lens  208  of the imager  202  directly faces a reflector  210  in such a manner as to capture an image of the operator&#39;s profile, P, with reflected optics. As seen more clearly in  FIG. 3 , when located in the recessed bezel  304 , the optical system  300  may be closed-out by a tinted, but optically transparent panel  316  such that the vehicle operator is not able to notice the presence of the optical system  300 . 
   Referring to both  FIGS. 3 and 4A , the optical system  300  is shown in greater detail. The optical system  300  is based upon the general representations shown in  FIGS. 1A and 2B  in that an imager  302  is positioned within the recessed bezel  304  of a valance panel  306  with co-located illuminators  308 . As illustrated, an array of sixteen illuminators  308  are shown in four-by-four matrix to the left of the imager  302 ; however, the optical system  300  is not limited to a specific number of illuminators  308  in any specific location or position. For example, one illuminator  308  or the four-by-four matrix of illuminators  308  may be positioned about the A-pillar  310 . Alternatively, if co-located with the imager  302 , the illuminators  308  may be positioned to the right of the imager  302  ( FIG. 4B ), forwardly of the imager  302  ( FIG. 4C ), or around the imager  302  in a horseshoe-type configuration ( FIG. 4D ). 
   If the illuminator(s)  308  is/are co-located with the imager  302 , an integral package may be achieved that results in a reduction of wiring and installation time of the optical system  300 . Although an embodiment showing illuminators  308  positioned rearwardly of the imager  302  is not shown, such an embodiment may be implemented. However, in referring to  FIG. 5 , if illuminators  308  were to be positioned rearwardly of the imager  302 , the vertical distance, Z, that is relative to the position of the imager  302  and reflector  310  is increased (i.e., the reflector will reside in a higher position on the windshield  312 ). Because the reflector  310  may not be entirely transmissive (i.e., the reflector  310  may be approximately 90% transparent), the reflector  310  may become optically noticeable to the vehicle operator and appear to be a smudge or blur on the windshield  312 . As a result, it may be preferable to locate the imager  302  as close to the windshield  312  as possible (i.e., reduce the horizontal distance, X, that is relative to the position of the imager  302  and the windshield  312 ). 
   According to an embodiment of the invention, the horizontal distance, X, may be any desirable length ranging approximately between zero and twelve inches. Because the vertical distance, Z, is dependent upon the length of the horizontal distance, X, due to curvature of the windshield glass  312  and slope of the valance panel, the vertical distance, Z, should be reduced such that the reflector  310  is not noticeable to the vehicle operator, as described above. According to an embodiment, a horizontal distance, X, may be selected such that the vertical distance, Z, is within any desirable length ranging approximately between zero and three inches. It will be appreciated that the invention is not limited to the dimensions described above and that the invention may be practiced by using any desirable dimensions that defines the vertical distance, Z, and the horizontal distance, X. Accordingly, as seen in  FIG. 6A , when the vertical and horizontal distances, X, Z, are reduced, the aspect ratio of the operator&#39;s profile, P, is reduced, and, in reference to  FIG. 6B , when the vertical and horizontal distances X, Z, are increased, the aspect ratio of the operator&#39;s profile, P, is increased. In situations when a larger profile, P, is called for, the general surface area of the reflector  310  is correspondingly increased as well. 
   Referring to  FIG. 7 , a magnified view of the reflector  310  is shown according to an embodiment. In operation, the reflector  310  reflects infrared (IR) light and passes visible light. As illustrated, the reflector  310  comprises a relatively thin layer of substrate material  310   a  and a relatively thin layer of reflective film  310   b.  The substrate material  310   a  may be a quartz material, which is sold under the trade-name BOROFLOAT™, and the reflective film  310   b  consists of a multi-layer dielectric coating. The reflector  310  may be referred to in the art as a “Hot Mirror” and is commercially available from Edmund Industrial Optics of Barrington, N.J. The reflector may include any desirable thickness, T, such as, for example, that is approximately equal to one-tenth of a millimeter, and may include any desirable shape, such as, for example, a circular disc ( FIG. 3 ) or a rectangular sheet. According to an embodiment, if the reflector  310  is a circular disc, the diameter, D, may be approximately equal to 25 mm. The reflector  310  may be adhered to the windshield  312  with any type of adhesive. As such, the reflector  310  may be manufactured in a similar fashion as a sticker that is manually applied to the windshield  312 . 
   If the windshield  312  has an extreme curvature, the resultant image captured by the imager  302  may be unevenly magnified and distorted. However, if the windshield curvature is known, image distortion software (not shown) may treat the captured image to provide an expected, correct image. 
   In an embodiment, the imager  302  may be a Complementary Metal Oxide Semiconductor (CMOS) imager, or, alternatively, a Charge-Coupled-Device (CCD) imager, and the illuminators  308  may be IR illuminators. Although the above-described optics are related to IR light, the invention is not limited to process light in the IR spectrum. As such, the illuminators may comprise any type of incandescent light emitting diode or bulb, and the appropriate non-IR imager and reflector may be accordingly selected. 
   Depending on the horizontal distance, X, of the CMOS imager  302 , the CMOS imager  302  may include a field of view lens  314  ranging from +/−10 0 to ×/−35°. Referring to  FIG. 8 , as a result of the horizontal position, X, and the chosen field of view lens  314 , a head-box  400  that defines the aspect ratio of the captured operator profile, P, may be increased or reduced as desired. As such, the CMOS imager  302  may be limited to focusing on eye ellipses  402  in relation to the operator profile, P, illustrated in  FIG. 6A , or alternatively, the CMOS imager  302  may be allowed to capture an entire image of the operator profile, P, as shown in  FIG. 6B . 
   In reference to  FIG. 9A , a normalized CMOS imager response curve is shown. The x-axis of the diagram ranges from 400 nm to 1000 nm and the y-axis represents sensitivity on the order of 0% to 100%. Generally, the chart represents the number of photons the CMOS imager  302  collects, and, when held efficiently, the CMOS imager  302  turns the photons into electrons. As illustrated, the CMOS imager  302  typically peaks when receiving light in the visible light band between 400 nm and 700 nm. An absolute peak in sensitivity occurs approximately between the 500 nm and 600 nm range. As illustrated in the non-visible light range (i.e. Infrared light), the CMOS imager  302  is responsive to approximately half the peak sensitivity of light in the visible band. 
   According to the present embodiment of the invention, the IR illuminators  308  may be specified to emit light between the 850 nm and 950 nm range. Referring to  FIG. 9B , a normalized response curve of an IR light emitting diode (LED) is illustrated. To overcome any losses in the optical system  300 , an optimal wavelength for an IR illuminator LED  308  may be selected to be approximately equal to 850 nm (i.e., the center wavelength, according to  FIG. 9B ). Referring to  FIG. 9C , a normalized response curve of an IR band-pass filter is shown, and, accordingly, the optical system  300  may include a band-pass filter  22  that may be matched with the IR illuminator  308  to expect the appropriate CMOS imager response as shown in  FIG. 9A . As a result, if the IR illuminator  308  is illuminating at 850 nm and if the band-pass filter  22  only accepts 850 nm, the optical system  300  improves the ability to ignore natural, ambient lighting. 
   Accordingly, the above-described optical systems capture a center-lined, unobstructed image of the operator&#39;s profile, P, with reflected optics. If applied in an after-market situation ( FIG. 2A ) or if installed by an original equipment manufacturer ( FIG. 2B ), the optical system may be located in a position such that is discretely located or completely hidden from the sight of the vehicle operator and occupants. Even further, if installed by an original equipment manufacturer, the optical system may be located in a position proximate the valance panel and instrument panel ductwork. Accordingly, an area in the instrument cluster (FIGS.  10 A and  10 B), which is considered to be “prime real estate” for automotive interior designers, is completely avoided. Thus, an improved optical system is provided that may be packaged into a single, compact unit, may free up prime real estate in the instrument cluster area, and consistently provide an unobstructed image of the operator&#39;s profile with reflected optics as opposed to direct optics. 
   While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.