EXHIBIT 1006:
`
`WO 97/35743 FOR "VEHICLE HEADLIGHT CONTROL USING IMAGING
`
`SENSOR," ISSUED TO SCHOFIELD ET AL. ON OCTOBER 2, 1997
`
`("SCHOFIELD PCT")
`
`TRW Automotive U.S. LLC: EXHIBIT 1006
`PETITION FOR INTER PARTES REVIEW
`OF U.S. PATENT NUMBER 8,629,768
`
`

`

`PCT
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`WO 97/35743
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`(51) International Patent Classification 6 :
`B60Q 1114
`
`(11) International Publication Number:
`
`Al
`
`(43) International Publication Date:
`
`2 October 1997 (02.10.97)
`
`(21) International Application Number:
`
`PCf/US97/04829
`
`(22) International Filing Date:
`
`25 March 1997 (25.03.97)
`
`(30) Priority Data:
`08/621,863
`
`25 March 1996 (25.03.96)
`
`us
`
`(71) Applicant: DONNELLY CORPORATION [US/US]; 414 East
`Fortieth Street, Holland, MI 49323 (US).
`
`(81) Designated States: AL, AM, AT, AU, AZ, BB, BG, BR, BY,
`CA, CH, CN, CZ, DE, DK, EE, ES, FI, GB, GE, HU,
`IS, JP, KE, KG, KP, KR, KZ, LK, LR, LS, LT, LU, LV,
`MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT. RO, RU,
`SD, SE, SG, SI, SK, TJ, TM, TR, IT, UA, UG, UZ, VN,
`ARIPO patent (GH, KE, LS, MW, SD, SZ, UG), Eurasian
`patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European
`patent (AT, BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT,
`LU, MC, NL, PT, SE), OAPI patent (BF, BJ, CF, CG, CI,
`CM, GA, GN, ML, MR. NE, SN, TD, TG).
`
`(72) Inventors: SCHOFIELD, Kenneth; 4793 Crestridge Court,
`Holland, MI 49423 (US). LARSON, Mark, L.; 13873
`Oakwood Circle, Grand Haven, MI 49417 (US). VADAS,
`Keith, J.; 552 Harrison Avenue, Coopersville, MI 49404
`(US).
`
`Published
`With international search report.
`Before the expiration of the time limit for amending the
`claims and to be republished in the event of the receipt of
`amendments.
`
`(74) Agent: BURKHART, Frederick, S.; Van Dyke, Gardner, Linn
`& Burkhart, L.L.P., Suite 207, 2851 Charlevoix Drive, S.E.,
`Grand Rapids, MI 49546 (US).
`
`(54) Title: VEHICLE HEADLIGHT CONTROL USING IMAGING SENSOR
`
`(57) Abstract
`
`A vehicle head1amp control method and appa(cid:173)
`ratus includes providing an imaging sensor (14) that
`senses light in spatially separated regions of a field of
`view forward of the vehicle. Light levels sensed in in(cid:173)
`dividual regions of the field of view by a sensor array
`(38) are evaluated in order to identify light sources of
`interest, such as oncoming headlights and leading tail(cid:173)
`lights. The vehicle's headlights (18) are controlled by
`lighting control logic (16) in response to identifying
`such particular light sources or absence of such light
`sources. Spectral signatures of light sources may be
`examined in order to determine if the spectral signa(cid:173)
`ture matches that of particular light sources such as the
`spectral signatures of headlights or taillights. Sensed
`light levels may also be evaluated for their spatial dis(cid:173)
`tributions in order to identify light sources of interest.
`
`VEHICLE
`LIGHTING
`CONTROL
`LOGIC
`
`16
`
`20
`
`IB
`
`36
`
`13
`
`1006-001
`
`

`

`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCI' on the front pages of pamphlets publishing international applications under the PCI'.
`
`AL
`AM
`AT
`AU
`AZ
`BA
`BB
`BE
`BF
`BG
`BJ
`BR
`BY
`CA
`CF
`CG
`CH
`Cl
`CM
`CN
`cu
`cz
`DE
`DK
`EE
`
`Albania
`Annenia
`Austria
`Australia
`Azerbaijan
`Bosnia and Herzegovina
`Barbados
`Belgium
`Burlr.ina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`COte d'lvoire
`Cameroon
`China
`Cuba
`Czech Republic
`Gennany
`Denmark.
`Estonia
`
`ES
`Fl
`FR
`GA
`GB
`GE
`GH
`GN
`GR
`HU
`IE
`IL
`IS
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`LC
`Ll
`LK
`LR
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People's
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`LS
`LT
`LU
`LV
`MC
`MD
`MG
`MK
`
`ML
`MN
`MR
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`
`Lesolho
`Lithuania
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`The fonner Yugoslav
`Republic of Macedonia
`Mali
`Mongolia
`Mauritania
`Malawi
`Mexico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`
`Sl
`SK
`SN
`sz
`TD
`TG
`TJ
`TM
`TR
`TT
`UA
`UG
`us
`uz
`VN
`YU
`zw
`
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`Turlr.menistan
`Turkey
`Trinidad and Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`VietNam
`Yugoslavia
`Zimbabwe
`
`1006-002
`
`

`

`WO 97/35743
`
`PCTIUS97/04829
`
`VEHICLE HEADLIGHT CONTROL USING IMAGING SENSOR
`
`CROSS-REFERENCE TO RELATED APPLICATION
`
`This application is a continuation-in-part of co-pending application Serial No.
`
`08/023,918 filed February 26, 1993, by Kenneth Schofield and Mark Larson.
`
`5
`
`BACKGROUND OF THE INVENTION
`
`This invention relates generally to vehicle control systems and, in particular, to a system
`
`and method for controlling the headlights of the vehicles. The invention is particularly adapted
`
`to controlling the vehicle's headlamps in response to sensing the headlights of oncoming
`
`vehicles and taillights of leading vehicles.
`
`I 0
`
`It has long been a goal to automatically control the state of a vehicle's headlights in order
`
`to accomplish automatically that which is manually performed by the driver. In particular, the
`
`driver of a vehicle whose headlights are in a high-beam state will dim the headlights upon
`
`conscious realization that the headlights are a distraction to the driver of an oncoming vehicle or
`
`a leading vehicle. It is desirable to relieve the driver of such duties and thereby allow the driver
`
`15
`
`to concentrate on the driving task at hand. The ideal automatic control would also facilitate the
`
`use of high beams in conditions which allow their use, increasing the safety for the controlled
`
`vehicle as well as reducing the hazard caused by the occasional failure of the driver to dim the
`
`headlights when such headlights are distracting another driver.
`
`Prior attempts at vehicle headlight dimming controls have included a single light sensor
`
`20
`
`which integrates light in the scene forward of the vehicle. When the integrated light exceeds a
`
`threshold, the vehicle headlights are dimmed. Such approaches have been ineffective. The
`
`headlights of oncoming vehicles are, at least from a distance, point sources of light. In order to
`
`detect such light sources in an integrated scene, it is necessary to set a sufficiently low threshold
`
`of detection that many non-point-sources at lower intensities are interpreted as headlights or
`
`25
`
`taillights. Such prior art vehicle headlight dimming controls have also been ineffective at
`
`reliably detecting the taillights of leading vehicles. The apparent reason is that the
`
`characteristics ofthese two light sources; for example, intensity, are so different that detecting
`
`both has been impractical. In order to overcome such deficiencies, additional solutions have
`
`been attempted, such as the use of infrared filtering, baffling of the optic sensor, and the like.
`
`30
`
`While such modifications may have improved performance somewhat, the long-felt need for a
`
`commercially useful vehicle headlight dimming control has gone unmet.
`
`1006-003
`
`

`

`W097/3S743
`
`PCT/US97/048l9
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a vehicle control which is capable of identifying unique
`
`characteristics of light sources based upon a precise evaluation of light source characteristics
`
`made in each portion of the scene forward of the vehicle, in the vicinity of each light source, by
`
`5
`
`separating each light source from the remainder of the scene and analyzing that source to
`
`determine its characteristics. One characteristic used in identifying a light source is the spectral
`
`characteristics of that source which is compared with spectral signatures of known light sources,
`
`such as those of headlights and taillights. Another characteristic used in identifying a light
`
`source is the spatial layout of the light source. By providing the ability to identify the headlights
`
`10
`
`of oncoming vehicles and the taillights of leading vehicles, the state of the headlights of the
`
`controlled vehicle may be adjusted in response to the presence or absence of either of these light
`
`sources or the intensity of these light sources.
`
`This is accomplished according to an aspect of the invention by providing an imaging
`
`sensor which divides the scene forward of the vehicle into a plurality of spatially separated
`
`15
`
`sensing regions. A control circuit is provided that is responsive to the photosensors in order to
`
`determine if individual regions include light levels having a particular intensity. The control
`
`circuit thereby identifies particular light sources and provides a control output to the vehicle that
`
`is a function of the light source identified. The control output may control the dimmed state of
`
`the vehicle's headlamps.
`
`20
`
`In order to more robustly respond to the different characteristics of headlights and
`
`taillights, a different exposure period is provided for the array in order to detect each light
`
`source. In particular, the exposure period may be longer for detecting leading taillights and
`
`significantly shorter for detecting oncoming headlights.
`
`According to another aspect of the invention, a solid-state light imaging array is provided
`
`25
`
`that is made up of a plurality of sensors arranged in a matrix on at least one semiconductor
`
`substrate. The light-imaging array includes at least one spectral separation device, wherein each
`
`of the sensors responds to light in a particular spectral region. The control circuit responds to
`
`the plurality of sensors in order to determine if spatially adjacent regions of the field of view
`
`forward of the vehicle include light of a particular spectral signature above a particular intensity
`
`30
`
`level. In this manner, the control identifies light sources that are either oncoming headlights or
`
`leading taillights by identifying such light sources according to their spectral makeup.
`
`-2-
`
`1006-004
`
`

`

`W097135743
`According to another aspect of the invention, a solid-state light-imaging array is provided
`
`PCTIUS971048l9
`
`that is made up of a plurality of sensors that divide the scene forward of the vehicle into spatially
`
`separated regions, and light sources are identified, at least in part, according to their spatial
`
`distribution across the regions. This aspect of the invention is based upon a recognition that
`
`5
`
`headlights of oncoming vehicles and taillights of leading vehicles are of interest to the control,
`
`irrespective of separation distance from the controlled vehicle, if the source is on the central axis
`
`of travel of the vehicle. Oncoming headlights and leading taillights may also be of interest away
`
`from this axis, or off axis, but only if the source has a higher intensity level and is spatially
`
`larger. These characteristics of headlights and taillights of interest may be taken into
`
`I 0
`
`consideration by increasing the resolution of the imaging array along this central axis or by
`
`increasing the detection threshold off axis, or both. Such spatial evaluation may be implemented
`
`by selecting characteristics of an optical device provided with the imaging sensor, such as
`
`providing increased magnification central of the forward scene, or providing a wide horizontal
`
`view and narrow vertical view, or the like, or by arrangement of the sensing circuitry, or a
`
`15
`
`combination ofthese.
`
`The present invention provides a vehicle headlight control which is exceptionally
`
`discriminating in identifying oncoming headlights and leading taillights in a commercially
`
`viable system which ignores other sources of light including streetlights and reflections ofthe
`
`controlled vehicle's headlights off signs, road markers, and the like. The present invention
`
`20
`
`further provides a sensor having the ability to preselect data from the scene forward of the
`
`vehicle in order to reduce the input data set to optimize subsequent data processing. The
`
`invention is especially adapted for use with, but not limited to, photoarray imaging sensors, such
`
`as CMOS and CCD arrays.
`
`These and other objects, advantages, and features of this invention will become apparent
`
`25
`
`upon review of the following specification in conjunction with the drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Fig. I is a side elevation of a portion of a vehicle embodying the invention;
`
`Fig. 2 is a partial side elevation view and block diagram of a vehicle headlight dimming
`
`control system according to the invention;
`
`30
`
`Fig. 3 is a block diagram of the control system in Fig. 2;
`
`Fig. 4 is a layout of a light-sensing array useful with the invention;
`
`Fig. 5 is a block diagram of an imaging sensor;
`
`-3-
`
`1006-005
`
`

`

`W097/35743
`Fig. 6 is an alternative embodiment of an imaging sensor;
`
`Figs. 7a-7d are a flowchart of a control program;
`
`PCT/US97/04829
`
`Figs. 8a-8c are spectral charts illustrating spectra regions useful with the invention;
`
`Fig. 9 is the same view as Fig. 3 of another alternative embodiment;
`
`5
`
`Fig. 10 is the same view as Fig. 2 of an alternative mounting arrangement;
`
`Figs. 11 a-ll c are views forward of a vehicle illustrating different forms of spatial
`
`filtering; and
`
`Figs 12a and 12b are illustrations of use of the invention to detect particular atmospheric
`
`conditions.
`
`10
`
`DESCRIPTION OF THE PREFERRED EMBODIMENT
`
`Referring now specifically to the drawings and the illustrative embodiments depicted
`
`therein, a vehicle 1 0 includes a vehicle headlight dimming control 12 made up of an imaging
`
`sensor module 14 which senses light from a scene forward of vehicle 10, an imaging control
`
`circuit 13 which receives data from sensor 14, and a vehicle lighting control logic module 16
`
`15
`
`which exchanges data with control circuit 13 and controls headlamps 18 for the purpose of
`
`modifying the headlight beam (Figs. 1 and 2). Such control may be a binary control of the aim
`
`of the beam, such as by switching between lamps or lamp filaments, or may be a continuous
`
`variation of the aim of a single lamp more or less forward of the vehicle. The control may also
`
`control the intensity or pattern of the beam. Additionally, the lights of a vehicle equipped with
`
`20
`
`daytime running lights may be switched between a daytime running light condition and a low(cid:173)
`
`beam condition. Vehicle headlight dimming control 12 can perform a wide range of additional
`
`control operations on the vehicle, including turning the headlights ON and OFF, modifying the
`
`light intensity of the instrument panel, and providing an input to an electro-optic mirror system.
`
`Vehicle lighting control logic module 16 receives an input 20 from imaging control
`
`25
`
`circuit 13. In particular embodiments, such as ones which adj~st the state of the headlights
`
`between continuously variable states, module 16 may supply data to imaging control circuit 13,
`
`such as the speed of the vehicle, which may be combined with the data sensed by imaging sensor
`
`14 in establishing the state of headlights 18. In the illustrated embodiment, imaging sensor
`
`module 14 may be fixedly mounted in a housing 28 by a bracket 34 mounted to, or near, the
`
`30
`
`vehicle's windshield 32. Bracket 34 also mounts an interior rearview mirror 30. This is a
`
`preferred mounting for imaging sensor module 14 because the location within the interior of the
`
`vehicle substantially eliminates environmental dirt and moisture from fouling the light sensor
`
`-4-
`
`1006-006
`
`

`

`W097/35743
`module. Additionally, the position behind windshield 32, which typically is kept relatively clear
`
`PCTIUS97/04829
`
`through the use of washers and wipers and the like, ensures a relatively clear view of the scene
`
`forward ofvehicle IO. Alternatively, imaging sensor module 14 may be mounted within a
`
`housing 29 of interior rearview mirror 30 facing forward with respect to vehicle I 0 (Fig. 1 0). In
`
`5
`
`such embodiment, control circuit 13 may be combined with the circuit which controls the partial
`
`reflectance level of mirror 30 if mirror 30 is an electro-optic mirror such as an electrochromic
`
`mirror. Other mounting techniques for sensor module I4 will be apparent to the skilled artisan.
`
`Imaging sensor module I4 includes an optical device 36, such as a lens, an array 38 of
`
`photon-accumulating light sensors, and a spectral separation device for separating light from the
`
`10
`
`scene forward of vehicle I 0 into a plurality of spectral bands, such as a filter array 40 disposed
`
`between optical device 36 and light-sensing array 38. Light-sensing array 38 is described in
`
`detail in co-pending application Serial No. 08/023,9I8 filed February 26, 1993, by Kenneth
`
`Schofield and Mark Larson for an AUTOMATIC REARVIEW MIRROR SYSTEM USING A
`
`PHOTOSENSOR ARRAY, the disclosure of which is hereby incorporated herein by reference.
`
`I5
`
`Light-sensing array 36 includes a plurality of photosensor elements 42 arranged in a matrix of
`
`columns and rows (Fig. 4 ). In the illustrated embodiment, an array of 5I2 rows and 5I2
`
`columns of light-sensing pixels, each made up of a photosensor element 42 is utilized.
`
`However, a greater or lesser number of photosensor elements may be utilized and may be
`
`arranged in matrix that is laid out in other than columns and rows. Each photosensor element 42
`
`20
`
`is connected to a common word-line 44. To access the photosensor array, a vertical shift register
`
`46 generates word-line signals to each word-line 44 to enable each row of photosensor elements
`
`42. Each column of photosensor elements is also connected to a bit-line 48 which is connected
`
`to an amplifier 50. As each word-line 44 is accessed, a horizontal shift register 52 uses a line 54
`
`to output the bit-line signals on consecutive bit lines 48 to an output line 56. In this manner,
`
`25
`
`each photosensor element 42 may be individually accessed by appropriate manipulation of shift
`
`registers 46 and 52. Output 56 is supplied to a digital signal processor I3 which is supplied on
`
`an output 62 as input to control circuit I3 (Figs. 3-5).
`
`Digital signal processor I3 includes an analog-to-digital converter 58 which receives the
`
`output 56 of array 36 and converts the analog pixel values to digital values. A digital output 68
`
`30
`
`of AID converter 58 is supplied to a taillight detection circuit 76, a headlight detection circuit 78,
`
`and to ambient sense logic circuit 84. A detection control circuit 72 supplies control and timing
`
`signals on a line 74 which is supplied to array 38, AID converter 58 taillight detection circuit 76,
`
`-5-
`
`1006-007
`
`

`

`W097/35743
`headlight detection circuit 78, and ambient sense logic 84. Such signals coordinate the activities
`
`PCT/US97/04829
`
`of these modules and provide any data, from look-up tables provided in control circuit 72,
`
`needed by each circuit to perform its function. For example, control circuit 72 may provide
`
`intensity threshold levels to taillight detection circuit 76 and headlight detection circuit 78.
`
`5
`
`Taillight detection circuit 76 detects a red light source having an intensity above a
`
`particular threshold as follows. For each pixel that is "red," a comparison is made with adjacent
`
`"green" pixels and "blue" pixels. If the intensity of a red pixel is more than a particular number
`
`oftimes the intensity of the adjacent green pixel and adjacent blue pixel, then it is determined
`
`that the light source is red. If the intensity of the ''red" light source is greater than a particular
`
`10
`
`threshold, an indication is provided at 80.
`
`Headlight detection circuit 78 detects a white light source having an intensity above a
`
`particular threshold as follows. A white light is a combination of red, green, and blue
`
`components. If adjacent "red," "green," and "blue" pixels all exceed a particular threshold, a
`
`ratio comparison is made of the pixels. If the ratio of the intensity of the adjacent "red,"
`
`15
`
`"green," and "blue pixels is within a particular range, such as 20 percent by way of example,
`
`then a white light source is detected.
`
`Vehicle headlight dimming control 12 additionally includes an ambient light-sensing
`
`circuit 84 which receives an input from digital output signal68. Ambient detection circuit 84
`
`samples a subset of photosensor elements and detects light levels sensed by the subset over a
`
`20
`
`long period oftime in order to produce significant time filtration. Preferably, the photosensor
`
`elements in the sensed subset include sensors that detect portions of the forward-looking scene
`
`that are just above the earth's horizon which is more indicative of the ambient light condition.
`
`Ambient detection circuit 84 produces an indication 88 of ambient light levels which is supplied
`
`as an input to a lighting control module 90. A high ambient light level may be used by a module
`
`25
`
`90 to inhibit headlight actuation or to switch headlights 18 to a daytime running light mode.
`
`Ambient detection circuit 84 can, optionally, perform other functions, such as switching the
`
`daytime running lights of the vehicle between daytime and nighttime modes, controlling the
`
`intensity of the vehicle's instrument panel and providing an input to an electro-optic rearview
`
`mirror system.
`
`30
`
`Indications 80 and 82 from the light detection units and indication 88 from ambient
`
`detection circuit 84 are supplied to a lighting control circuit 90 which produces a first indication
`
`92 that headlights 18 are to be switched on, or switched from a daytime running condition to a
`
`-6-
`
`1006-008
`
`

`

`W097/35743
`night mode, and a high-beam enable indication 94 that the headlights may be switched to a high(cid:173)
`
`PCTIUS97/04829
`
`beam state. Vehicle lighting control logic module 16 responds to indications 92 and 94 by
`
`switching headlights 18 to an appropriate mode. An output 96 from module 16 may be provided
`
`to supply lighting control circuit 90 with information with respect to vehicle telemetry, steering,
`
`5
`
`speed, and any other parameter that may be incorporated into the algorithm to determine the
`
`state ofthe headlights ofthe vehicle. Digital signal processor 13 may be implemented using
`
`discrete digital circuit modules or with a suitably programmed micro-processor with input and
`
`output buffers.
`
`In one embodiment, an imaging sensor module 14a includes a single photosensor array
`
`10
`
`38a, one spectral filter array 40a, and one optical device 36a (Fig. 5). In this illustrated
`
`embodiment, spectral filter array 40a includes alternating spectrum filter elements for exposing
`
`adjacent pixels to different regions of the electromagnetic spectrum in the red band or green
`
`band or blue band. This may be accomplished by arranging such filter elements in stripes or by
`
`alternating filter spectral regions in a manner known in the art. Digital signal processor 13a
`
`15
`
`captures a frame of data by enabling photosensor array 38a for a particular exposure period
`
`during which each photosensor element 42 accumulates photons. In order to detect oncoming
`
`headlights, digital signal processor 13a enables photosensor array 38a for a first exposure period.
`
`In order to detect leading taillights, digital signal processor 13a enables photosensor array 38a
`
`for a second exposure period. Because oncoming headlights have an intensity level that is
`
`20
`
`substantially greater than that of leading taillights, the exposure period of the frame in which
`
`leading taillights is detected is at least approximately ten times the length of the exposure period
`
`during which oncoming headlights are detected. Most preferably, the exposure period for
`
`detecting leading taillights is approximately 40 times the exposure period for detecting
`
`oncoming headlights. In the illustrated embodiment, an exposure period of 0.004 seconds is
`
`25
`
`utilized for detecting taillamps and 0.0001 seconds for detecting oncoming headlamps. The
`
`exposure period is the time during which each photosensor element 42 integrates photons before
`
`being read and reset by digital signal processor 13a. Establishing a different exposure period for
`
`detecting headlights verses taillights facilitates the use of existing and anticipated sensor
`
`technology by accommodating the dynamic range of such sensor technology. Exposure may
`
`30
`
`also be adaptively established on a priority basis. In one such embodiment, exposure is set to a
`
`shorter headlight setting. If headlights are detected, the headlights 18 of vehicle 1 0 are dimmed
`
`and the exposure period is kept short. If no headlights are detected, the next frame is set to a
`
`-7-
`
`1006-009
`
`

`

`W097/35743
`longer exposure period. This has the advantage of shorter system cycle time as well as a
`
`PCTIUS97/04829
`
`reduction in sensitivity to sensor saturation and blooming. In another such embodiment, the
`
`exposure period is initially set to a long period. If an oncoming headlight is tentatively detected,
`
`the exposure period could then be switched to a short period to confirm the observation.
`
`5
`
`Vehicle headlight dimming control12 carries out a control routine 100 (Figs. 7a-7d). At
`
`the beginning of each pass through the routine, which occurs for every frame captured by the
`
`imaging sensor, a frame is grabbed at I 02 and all of the pixels in the frame are processed as
`
`follows. Counters used for detecting white headlight sources and red taillight sources are zeroed
`
`at I 04. It is then determined at I 06 whether the previously processed frame was for detecting
`
`10
`
`headlights or taillights. This is determined by looking at a variable "process. tails" which will be
`
`set to "yes" if the previous frame was processed to detect headlights and will be set to "no" if the
`
`previous frame was processed to detect taillights. If it is determined at 1 06 that the variable
`
`"process. tails" is set to "yes," the control proceeds to 108 in order to process the next frame to
`
`detect taillights. If it is determined at 106 that the variable process .tails is set to "no," then
`
`15
`
`control passes to 1 09 in order to process the next frame as a headlight detecting frame.
`
`The taillight detecting frame process begins at I 08 by setting the exposure period for the
`
`imaging sensor module to grab the next frame according to a headlamp exposure level. In the
`
`illustrated embodiment, the exposure period for detecting headlights is set at 0.0001 seconds.
`
`Processing of the taillight frame proceeds at 110 by examining, for each "red" pixel, whether the
`
`20
`
`intensity of light sensed by that pixel is greater than a threshold and whether the intensity of
`
`light sensed by that pixel is greater than a selected number of multiples of the intensity of light
`
`sensed by an adjacent "blue" pixel and a selected number of multiples of the intensity of light
`
`sensed by an adjacent "green" pixel. If so, then a "red" counter is incremented at 114.
`
`Preferably, the ratio of red pixel intensity to green or blue pixel intensity is selected as a power
`
`25
`
`of 2 (2, 4, 8, 16 ... ) in order to ease digital processing. However, other ratios may be used and
`
`different ratios can be used between red/green and red/blue pixels. In the illustrated
`
`embodiment, a ratio of 4 is selected based upon ratios established from CIE illuminant charts
`
`known to skilled artisans. Based upon these charts, a ratio greater than 4 would provide greater
`
`discrimination. Such greater discrimination may not be desirable because it could result in
`
`30
`
`failure to identify a leading taillight and, thereby, a failure to dim the headlights of the controlled
`
`vehicle. After all pixels have been processed, the parameter "process.tails" is set to "no" at I16
`
`and control proceeds to 1I8 (Fig. 7c).
`
`-8-
`
`1006-010
`
`

`

`W097/35743
`In a similar fashion, processing of a headlight frame begins at 110 by setting the
`
`PCTJUS97104829
`
`exposure period for the imaging sensor module to grab the next frame as a red taillight detecting
`
`frame. This is accomplished by setting the exposure period of the imaging sensor module to
`
`0.004 seconds. It is then determined at 120 for each pixel whether an adjacent set of"red,"
`
`5
`
`"green," and "blue" pixels each exceeds a particular threshold and whether the pixel intensity
`
`levels all fall within a particular range, such as within 20 percent of each other. If all of the red,
`
`green, and blue pixels exceed a threshold and pass the ratio test, then it is determined that a
`
`white light source is being sensed and a "white" counter is incremented at 122. After all of the
`
`pixels in the frame have been processed, the process.tails flag is set to a "yes" state at 124.
`
`10
`
`Control then passes to 118.
`
`It is determined at 118 whether both the "white" and the "red" counters are below
`
`respective high-beam thresholds. If so, a high-beam frame counter is incremented and a low(cid:173)
`
`beam frame counter is set to zero at 120. If it is determined at 118 that both the "white" and the
`
`"red" counters are not less than a threshold, it is then determined at 126 whether either the "red"
`
`15
`
`counter or the "white" counter is greater than a respective low-beam threshold. If so, the high(cid:173)
`
`beam frame counter is set to zero and the low-beam frame counter is incremented at 128. If it is
`
`determined at 126 that neither the "red" counter or the "white" counter is greater than the
`
`respective low-beam threshold, then both the high-beam frame counters and the low-beam frame
`
`counters are set to zero at 130.
`
`20
`
`Control then passes to 132 where it is determined if the low-beam frame counter is
`
`greater than a particular threshold. If so, high-beam enable signal 94 is set to a "low-beam" state
`
`at 134. Additionally, the low-beam frame counter is set to the threshold level. If it is
`
`determined at 132 that the low-beam frame counter is not greater than its threshold, it is
`
`determined at 136 whether the high-beam frame counter is greater than its threshold. If so, high-
`
`25
`
`beam enable signal 94 is set to "high-beam" state at 138 and the high-beam frame counter is
`
`reset to its threshold level.
`
`Control routine 1 00 provides hysteresis by requiring that a headlight spectral signature or
`
`a taillight spectral signature be detected for a number of frames prior to switching the headlights
`
`to a low-beam state. Likewise, the absence of a detection of an oncoming headlight or a leading
`
`30
`
`taillight must be made for multiple frames in order to switch from a low-beam to a high-beam
`
`state. This hysteresis guards against erroneous detection due to noise in a given frame and
`
`eliminates headlamp toggling when sources are at the fringe of detection range. In the illustrated
`
`-9-
`
`1006-011
`
`

`

`W097135743
`embodiment, it is expected that a vehicle headlight control system 12 will respond to a change in
`
`PCTfUS97/04829
`
`the state of light sources in the forward field of view of the vehicle in less than 0.5 seconds. An
`
`additional level of hysteresis may be provided by forcing the headlamps to stay in a low-beam
`
`state for a given number of seconds after a transition from high beams to low beams. The
`
`5
`
`reverse would not occur; namely, holding a high-beam state for a particular period to avoid
`
`annoyance to drivers of oncoming or leading vehicles.
`
`In the illustrated embodiment, red light sources, which have the spectral signature and
`
`intensity of taillights, are detected by determining that a "red" pixel, namely a pixel which is
`
`exposed to light in the visible red band, is both greater than a given multiple ofthe "green" and
`
`10
`
`"blue" adjacent pixels, as well as being greater than a threshold and that white light sources,
`
`which are the spectral signatures of headlights, are detected by determining that "red," "green,"
`
`and "blue" pixels are both within a particular intensity range of each other as well as being
`
`greater than a threshold. This double-testing helps to reduce false detection of light sources.
`
`However, it would be possible to detect red light sources only by looking at the intensity of
`
`I 5
`
`"red" pixels and to detect white light sources by determining that an adjacent set of "red,"
`
`"blue," and "green"pixels are all above a particular threshold.
`
`In the illustrated embodiment, spectral filtering is carried out in a manner which exposes
`
`each photosensing element in the photosensor array to a band of light falling within o