PATENT DOCUMENT

Abstract:
The present invention relates to improved image sensor-processor interconnections and to monitoring and automatic control systems incorporating the improved image sensor-processor interconnections.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority, under 35 U.S.C. §119(e), to U.S. provisional patent application Ser. No. 60/448,793, filed on Feb. 21, 2003, and 60/495,906, filed on Aug. 18, 2003. The disclosures of these provisional patent applications are incorporated herein in their entireties by reference. 
    
    
     BACKGROUND 
     Vehicle monitoring and automatic equipment control systems have been proposed that incorporate image sensor technology. Typically, these systems are configured to acquire images of a desired scene and present the images to a vehicle driver and, or, occupant on a display. Often times these systems additionally, or in lieu of a display, process the electronic image information to automatically control vehicle equipment. 
     What are needed are improved vehicle monitoring and automatic equipment control systems. 
     SUMMARY 
     Vehicle monitoring and automatic equipment control systems in accordance with the present invention provide improvements to known systems. In at least one embodiment, a vehicle monitoring and automatic equipment control system incorporates a number of discrete components into integrated devices. 
     In at least one embodiment an improved imager is provided. 
     In at least one embodiment an improved enhanced transceiver is provided. 
     In at least one embodiment an improved imager interconnection with a mother board and, or, daughter board is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a plan view of a controlled vehicle relative a leading vehicle, an oncoming vehicle and another vehicle on a roadway; 
         FIG. 2  depicts a plan view of an embodiment of a controlled vehicle; 
         FIG. 3   a  depicts a perspective view of an embodiment of an accessory and rearview mirror assembly; 
         FIG. 3   b  depicts a second perspective view of the accessory and rearview mirror assembly of  FIG. 3   a;    
         FIG. 4  depicts a block diagram for an embodiment of an automatic equipment monitoring and control system; 
         FIG. 5   a  depicts a plan view of an embodiment of a mother board, a daughter board and an imager board interconnected with one another; 
         FIG. 5   b  depicts a second plan view of the opposite side of the mother board and daughter boards of  FIG. 5   a;    
         FIG. 6   a  depicts an embodiment of an imager board and interconnecting cable; 
         FIG. 6   b  depicts a second view of the imager board and interconnecting cable of  FIG. 6   a  with typically enclosed, non-visible, portions of the interconnecting cable exposed; 
         FIG. 7   a  depicts a block diagram of an embodiment of an imager; 
         FIG. 7   b  depicts an embodiment of an image sensor and temperature sensor; 
         FIG. 7   c  depicts imager related signal waveforms; 
         FIG. 7   d  depicts an imager command/response sequence; 
         FIGS. 7   e  and  7   f  depict a temperature sensor; 
         FIG. 8   a  depicts a block diagram of an embodiment of a low voltage differential signal device with memory; 
         FIG. 8   b  depicts an exploded view of an embodiment of a silicon wafer comprising a low voltage differential signal device with memory, wire bonds and external connection pins; 
         FIG. 8   c  depicts the pin configuration for an embodiment of a low voltage differential signal device with memory; 
         FIG. 8   d  depicts processor signal waveforms; 
         FIG. 8   e  depicts LVDS signal waveforms; 
         FIGS. 9   a - 9   j  depict various imager and processor configuration embodiments; 
         FIG. 10  depicts a plan view of a second embodiment of a mother board, a breakaway board and an imager board interconnected; 
         FIG. 11   a  depicts a plan view of a third mother board; and 
         FIG. 11   b  depicts a second plan view of the mother board of  FIG. 11   a.    
     
    
    
     DETAIL DESCRIPTION 
     Electronic image sensors vision systems and related automatic control systems have many potential applications in automobiles. For example, automatic vehicle exterior light control systems have been developed utilizing generally forward looking image sensors to detect the presence of other vehicles and automatically control exterior lights of a controlled vehicle to avoid imposing glaring light rays upon other drivers. Several other applications have been proposed or developed including: moisture sensing, adaptive cruise control, accident reconstruction systems, blind spot warning, night vision systems, rear vision systems, collision avoidance systems, lane departure warning systems, security systems, cabin monitoring systems, and others. 
     Such systems can generally be divided into two categories, those with a primary purpose of presenting an image, or series of images, to the driver of a controlled vehicle and those in which an image, or series of images, is analyzed by a processor in order to automatically perform some vehicle equipment related function. Some systems may provide both functions and in other systems a processor may enhance or augment a displayed image. In either case, it is almost always necessary to transmit an image signal from an imager to a processor and, or, display. In many embodiments of the present invention the transmitted image is a digitized image signal. 
     In some applications, the processor, and, or display to which the image is transmitted is located some distance from the imager. For example, consider an embodiment of an automatic vehicle exterior light control system integrated into an automatic dimming rear-view mirror. The imager is preferably located in an accessory module mounted to an attachment member to insure that the aim of the imager remains independent of a rearview mirror aim adjustment as disclosed in commonly assigned U.S. Patent Application Publication No. 2004/0164228 and U.S. Provisional Patent application Ser. No. 60/448,793. A processor is preferably located on a mother board housed in the mirror housing. The processor may be configured to perform additional functions such as controlling the reflectance of an electro-optic mirror element, a compass, a voice recognition processor, a telemetry system, a telephone, an information displays, an information display driver, operator interfaces indicators, or the like. The image data must be transmitted from the imager board to the mother board on which the processor is located. Other examples of remote imager locations are readily apparent. One or more image sensors may be located in various places in, or on, a controlled vehicle to monitor various fields of view. These imagers may transmit data to one or more processors centrally located or distributed throughout the vehicle. These image sensors may transmit images to one or more displays that may be located in convenient viewing positions for the driver and, or, occupants. 
     In the environment of a typical vehicle, it is desirable to manage electromagnetic interference (EMI). This includes both limiting the radiated emissions from an electronic device, as well as, insuring that the device is not susceptible to emissions from other sources. Stringent requirements are often imposed by automobile original equipment manufactures (OEMs) that require testing and measuring emissions from a device as well as tests in which a device is subjected to an electromagnetic field to insure the device does not malfunction. 
     Designing an electronic vision system to meet these requirements is a difficult challenge. This is due largely to the high data rates associated with transmitting digital images. A typical electronic image sensor may contain anywhere from a few thousand to over a million pixels, each of which having an output that is typically digitized at 8 or 10 bits. In many of the applications described herein, several images are acquired and transmitted every second. This results in digital data transmission rates from several kilo-baud to several mega-baud. This high data transmission rate can produce high levels of electromagnetic radiation. One method to reduce the data transmission rate is disclosed in commonly assigned U.S. patent application Ser. No. 60/531,484, entitled One-Zero Serial Communication, filed on Dec. 19, 2003, the entire disclosure of which is incorporated herein in its entirety by reference. The mother board/imager board interconnections described herein provide additional electromagnetic interference advantages. 
     In many cases it is desirable to have multiple vision systems performing multiple functions or multiple image sensors providing multiple views to the driver. For example, a driver would benefit from having both an automatic exterior light control system and a moisture sensing system to automatically control a vehicle&#39;s exterior lights its windshield wipers and, or, defogger. Automatic vehicle exterior light control systems are described in commonly assigned U.S. Pat. Nos. 5,990,469, 6,008,486, 6,130,421, 6,130,448, 6,255,639, 6,049,171, 5,837,994, 6,403,942, 6,281,632, 6,281,632, 6,291,812 and U.S. patent applications Ser. Nos. 09/448,364, 09/538,389, 09/605,102, 09/678,856, 09/800,460, 09/847,197, 09/938,774, 09/491,192, 60/404,879, 60/394,583, 10/235,476, 10/208,142, the disclosures of which are incorporated in their entireties herein by reference. Automatic moisture sensing systems are described in commonly assigned U.S. Pat. Nos. 5,923,027 and 6,313,457 and U.S. patent applications Ser. Nos. 09/970,962 and 09/970,728, the disclosures of which are incorporated in their entireties herein by reference. 
     An imager for an automatic exterior light control system is preferably focused for far-field imaging to detect headlights of oncoming vehicles and taillights of leading vehicles and further preferably has color discrimination capability to distinguish red light sources from other objects. An imager for a moisture sensing system is preferably focused on the windshield (near field) to image the moisture and preferably has a wide field of view. One option to solve these conflicting requirements is to provide a variable lens that can be switched to perform each function. Another option is to provide a lens with high depth of field that images both near-field moisture and far-field light sources. Complex software methods are typically employed when such lens systems are incorporated to distinguish near and far field objects. 
     To optimally perform both functions it is advantageous to employ two separate imagers, each with optics designed for a specific function. At least one embodiment of the present invention provides an economically efficient method of sharing substantially all support electronics and mechanical structures to allow a second imager to be added very cost efficiently. The incremental cost for the second imager may be the cost of the image sensor and optics, which is typically a small fraction of the total cost. Other applications requiring multiple imagers use stereoscopic vision wherein two imagers are used spaced apart from one another to provide capability for accurate distance measurement of objects. The techniques presented herein are also advantageous for these applications. Finally, the techniques of the present invention may also be used to add a third or more imager. 
     Turning now to  FIG. 1 , an embodiment of a controlled vehicle  105  having an accessory and rearview mirror assembly  106 , exterior light rays  107  and a glare area  108  is depicted on a divided highway  100 . The controlled vehicle is shown in relationship to a leading vehicle  110  having taillight rays  111  and an oncoming vehicle  115  having headlight rays  116 . 
     With additional reference to  FIG. 2 , an embodiment of a controlled vehicle  205  is depicted as comprising an accessory and rearview mirror assembly  206 . The controlled vehicle also has a driver&#39;s side rearview mirror assembly  210   a  and a passenger&#39;s side rearview mirror assembly  210   b . Preferably, the rearview mirror assemblies comprise electro-optic mirror elements as described in many commonly assigned U.S. Patents and Patent Applications. The controlled vehicle further comprises headlight assemblies  220   a ,  220   b ; front foul weather lights  230   a ,  230   b ; front turn signal/hazard indicators  235   a ,  235   b ; taillight assemblies  225   a ,  225   b ; rear turn signal indicators  226   a ,  226   b ; rear hazard indicators  227   a ,  227   b ; backup indicators  240   a ,  240   b  and a center high mounted stop light (CHMSL). Preferably, the headlight assemblies are bi-xenon and, or, repositionable. It should be understood that the controlled vehicle may comprise additional exterior lights, may comprise various combinations of the exterior lights depicted in  FIG. 2  or may combine any of the exterior lights shown in  FIG. 2  with additional exterior lights. It should be understood that any of the exterior lights may be provided with dimming means, repositioning means, focusing means, color changing means, aiming means or combinations thereof for altering an associated exterior light characteristic. With further reference to  FIG. 2 , the controlled vehicle comprises A-pillars  250   a ,  250   b ; B-pillars  255   a ,  255   b  and C-pillars  260   a ,  260   b . It should be understood that any of the lighting assemblies, rearview mirror assemblies, pillars or combinations thereof provide suitable mounting locations for additional imagers, or for an imager in lieu of, an imager in the accessory and rearview mirror assembly  206 . It should be understood that any imager assembly may comprise a repositioning means for selectively obtaining alternate desired fields of view with a single imager. An imager may be configured to be automatically repositioned as a function of at least one pitch sensor, at least one yaw sensor, at least one steering sensor, at least one speed sensor, any one thereof, a subcombination or combination thereof. 
     Turning now to  FIGS. 3   a  and  3   b , there is shown an embodiment of an accessory and rearview mirror assembly  306   a ,  306   b . The accessory and rearview mirror assembly comprises a stationary housing  377   a ,  377   b  and a repositional mirror housing  375   a ,  375   b  mounted to an attachment member  381   a ,  381   b . Preferably, the stationary housing contains at least one imager board, at least one processor, at least one compass sensor, at least one supplemental light source, at least one moisture sensor, at least one automatic exterior light control circuit, at least one microphone, at least one speaker, any one thereof, a sub-combination thereof or combinations thereof. Preferably, the repositional mirror housing  375   a ,  375   b  contains an electro-optic mirror element  322   a , at least one electro-optic mirror element automatic drive control circuit, a daytime running light automatic control circuit, an automatic exterior light control circuit; at least one information display  388   a ,  389   a , at least one glare light sensor  396   a ,  397   a , at least one indicator  386   a ,  387   a , at least one operator interface  391   a , at least one microphone  365   b , at least one ambient light sensor  387   b , at least one wire harness  398   b  and at least one vehicle equipment connector  399   b . The accessory and rearview mirror assembly may also comprise a bezel  390   b  and, or, an extended viewing area mirror element  345   a . It should be understood that a wire harness  398   b  may be routed out of the repositional mirror housing  375   a ,  375   b , through a first pivot ball  376   b   1 , mounting stem  376   b   2  and through a second pivot ball (not shown) into the stationary housing  377   a ,  377   b.    
     With reference now to  FIG. 4 , there is depicted a block diagram of an embodiment of an automatic vehicle equipment control system  400 . As can be seen, an imager  405  is configured to communicate with a processing and control system  410  via a communication interface  415 . It should be understood that the communication interface may be hardwired, radio frequency, fiber optics, light ray, sub-combinations thereof or combinations thereof. The processing and control system comprises at least one processor  420 , at least one ambient light sensor, at least one glare light sensor  430 , at least on electro-optic mirror element automatic drive control circuit  435 , at least one electro-optic mirror element automatic drive control output  440 , at least one information display output  445 , at least one exterior light status indicator output  450 , at least one pedestrian/bicyclist status indicator output  455 , at least one pedestrian/bicyclist indicator override switch input  460 , at least one windshield wiper and, or, defogger output  465 , a controlled vehicle speed input  470 , at least one electro-optic element reverse override input  475 , at least one automatic/on/off switch input  480 , at least one manual dimmer switch input  485 , at least one vehicle bus interface  490 , at least one exterior light controller output  491 , at least one compass sensor input  471 , any one thereof, a subcombination thereof or a combination thereof. The exterior light controller  495  may comprise a plurality of individual outputs  496  for independent control of various exterior lights  499 . It should be understood that additional components, inputs and outputs may be provided and, or, individual components may be integrated with one another in subassemblies. For example, an exterior light assembly may comprise at least one light ray source, a repositioning means, a focusing means, an aiming means, a color changing means, a light ray emission control means, etc. The exterior light assembly may be configured to connect to a processing and control interface, such as a vehicle bus or the like, and to a vehicle electrical power source. It should be understood that a plurality of vehicle equipment sensor outputs are available from a vehicle data communication bus. It is preferable to acquire any desired sensor data from these otherwise available vehicle devices. 
     Turning to  FIGS. 5   a  and  5   b , an embodiment of an automatic vehicle equipment control system assembly  500   a ,  500   b  is depicted to include a mother board  505   a ,  505   b , an imager board male receptacle connector  506   a , a vehicle equipment male receptacle connector  507   a ,  507   b , a processor  508   a , an enhanced transceiver  509   a , a vehicle bus communication chip  510   a , an ambient light sensor  511   a , a glare light sensor board  512   a , a glare light sensor  513   b , compass sensors  514   a , a first indicator  515 , a second indicator  516 , operator interface contacts  517 , operator interface indicators  518  and third indicator  519 . 
     The mother board is connected to a daughter board  520   a ,  520   b  via a mother board/daughter board interconnection  525   a ,  525   b . The daughter board comprises an information display driver  522   b  and an information display  521   b . As can be seen, the glare sensor board and the daughter board have at least one component that is oriented such that it faces an opposite direction from the components mounted directly to the mother board. It should be understood that the components of the glare sensor board and the daughter board may be mounted directly to the mother board on an opposite side from other mother board components. The configuration depicted in  FIGS. 5   a  and  5   b  is preferred for manufacturing processes related to this embodiment. It should be understood that the daughter board may be connected to the mother board similar to the imager board connection, via a radio frequency wireless interconnection, a fiber optic interconnection, a vehicle bus interconnection, a light ray interconnection or a combination thereof. The hard wire interconnection may be via a substantially flat, ribbon type, configuration; cables with individually shield twisted pairs; multiple individual cables or non-shielded conductors. 
     The mother board is also connected to an imager board  535   a  via a mother board/imager board interconnection  545   a . The imager board comprises a mother board male receptacle connector  536   a , an imager  537   a , a lens cover  538   a , a data LVDS  539   a , a clock LVDS  540   a , and lenses  541   a . The interconnection  545   a  comprises an imager board female plug connector  547   a , a mother board female plug connector  546   a  having a mechanical clip for snap interlock with the mating mother board male receptacle connector  506   a  and a ground connector  548   a . It should be understood that said imager board may comprise an imager board heater (not shown) configured to maintain the temperature of the imager board above ambient. This configuration is beneficial to inhibit condensation and the like from forming on an imager. It should be understood that the imager board heating may be on continuously or may be configured to be automatically controlled; for example, the temperature sensor on board the imager may be configured to operate an on board output such that no additional lines from a mother board to the imager board are required. 
     Turning now to  FIGS. 6   a  and  6   b , there are shown two embodiments of imager boards as elements  635   a ,  635   b  with mother board/imager board interconnections  645   a ,  645   b . The imager board  635   a  is similar to imager board  635   b  aside from the fact that the data and clock LVDSs are integrated into the imager  637   a . In preferred embodiments, the imager may have at least one of: an image sensor logic and control circuit; an analog-to-digital converter; a temperature sensor; an LVDS; a voltage regulator; a control output integrated on a common wafer with an image sensor. The mother board/imager board interconnection comprises a mother board female plug connector  646   a ,  646   b  with a mechanical clip  654   b , an imager board female plug connector  647   a ,  647   b , a first boot  650   a ,  650   b , a second boot  661   a , a jacket  661   b , a foil shield  649   b , a ground connector  648   a ,  648   b , a ground conductor  651   b , a first ground insulation  652   b , a second ground insulation  653   b , a positive conductor  655   b , a reference conductor  656   b , a second ground conductor  657   b , a first twisted pair  658   b , a second twisted pair  659   b  and a NSS conductor  660   b . It should be understood that the imager board may be connected to the mother board similar to the daughter board connection, via a radio frequency wireless interconnection, a fiber optic interconnection, a vehicle bus interconnection, a light ray interconnection or a combination thereof. A hardwire interconnection may be via a substantially flat, ribbon type, configuration; cables with individually shield twisted pairs; multiple individual cables or non-shielded conductors depending on the length, whether or not the conductors are within a “through the ball” configuration. 
     With reference to  FIGS. 7   a  and  7   b , an imager  737   a ,  737   b  is depicted to comprise: an image sensor  765   a ,  765   b ; temperature sensors  770   a ,  770   b ; dark pixels  798   b ; guard pixels  799   b ; image sensor logic and control circuit  766   a ; a pipelined analog-to-digital converter  767   a ; a 1-32× gain stage  768   a ; LVDS I/O  769   a ; voltage regulators  771   a ; a crystal oscillator interface  772   a ; analog column  773   a ; row decoders  774   a ; column decoders  775   a ; a reset boost  776   a ; digital-to-analog converters  777   a ; voltage/current references  778   a ; a 5V V DD  connection  779   a ; a MISO (for test) connection  780   a ; a MOSI connection  781   a ; an SPSCLK connection  782   a ; an NSS connection  783   a ; an OSC+ connection  784   a ; an OSC− connection  785   a ; a data out line  786   a ; control signals  787   a  for pipelined analog-to-digital converter  767   a ; control signals for biases  788   a ; power down  788   a ; control signals  789   a  for digital-to-analog converters  777   a ; a row number line  790   a ; a raw analog line  791   a ; control signals  792   a ; a column number line  793   a ; a gain control line  794   a ; amplified signals  795   a ; a 3.3V V DD  line  796   a  and a 3.3V V AA  line  797   a.    
     Turning to  FIGS. 7   e  and  7   f , there is shown a block diagram  705   e  and a VBE generator  715   e ,  715   f . Preferably, the temperature sensors are incorporated into the imager as described herein. Preferably, the temperature sensor comprises a bandgap  710   e , a V BG  line, a V-I converter  720   e , an I REF  line  721   e , a V BE2  line  725   e , a V BE1  line  730   e , a reference voltage generator  735   e , a V REF  line  740   e , a V REFADC  line  745   e , a first column address  750   e , a second column address  755   e , a temperature gain register  760   e , a gain  765   e  and an ADC  770   e . The VBE generator comprises a first transistor  775   f , a second transistor  780   f , a third transistor  795   f  and PNP structures  785   f ,  790   f . The current through PNP structure  790   f  is a multiple of the current through  790   f , for example, a factor of 64. The difference in the VBE between  785   f  and  790   f  is a function of the temperature. The VBE generator further comprises a Vaa connection  796   f , a vb 2  connection  797   f , an irefT connection  798   f , an AGND connection  789   f , a sampb_vbe 1  connection  786   f  and a sampb_vbe 2  connection  791   f . The analog gain  765   e  and ADC  770   e  are preferably the same devices as  768   a  and  767   a , respectively. Therefore, the temperature sensor values are read out identical to pixel values. 
     Following is a detail description of a preferred embodiment of an imager. As described, the imager incorporates a image sensor, temperature sensors, dark pixels, guard pixels, an image sensor logic and control circuit, voltage regulators, LVDSs, analog-to-digital converters, loop back testing features and a control output. The control output is particularly useful for moisture sensor applications incorporating supplemental illumination. 
     EXAMPLE IMAGER 
     This document describes an imager designed to meet the requirements of automotive locations. The image sensor provides 144 columns and 176 rows of photodiode based pixels. Control and data signals are communicated over a Low Voltage Differential Signaling Serial Peripheral Interface (LVDS SPI) connection to a processor. The imager also has provisions for sensing temperature, controlling one output signal, providing voltage regulation to internal components, and some device testing. 
     Commands provide control of a variety of exposure, mode, and analog settings. The imager is capable of taking two images simultaneously from different starting rows, a feature that permits highly synchronized images in a dual lens system. In this mode each image can have an independent gain setting. Another option allows the gains to be applied in a checkerboard image for applications where a spectral filter is applied to the image sensor in a checkerboard pattern. The imager also transmits a parity byte with the output data so the processor can verify the reception of the proper data. Data can be transmitted in ten bit mode, a compressed eight bit mode where a ten bit value is represented in eight bits, or a truncated eight bit mode where only the most significant eight bits of each ten bit pixel is transmitted. Table 1 depicts a series of specifications for the imager of this example. 
     
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
             
               
                 Resolution 
                 176 × 144 
               
               
                 Pixel Size 
                 15 μm × 15 μm 
               
               
                 Pixel Type 
                 Photodiode 
               
               
                 Sensitivity 
                 7 V/lux-sec 
               
               
                 Fill Factor 
                 &gt;70% 
               
               
                 ADC Resolution 
                 10-bits 
               
               
                 ADC Conversion Rate 
                 &gt;1 Msamples/sec 
               
               
                 ADC References 
                 Programmable 
               
               
                 Analog Gain 
                 1–32 Programmable 
               
               
                 Differential Output 
                 RS-644 
               
               
                 I/O Pad Size 
                 100 μm × 100 μm 
               
               
                 Clock Input 
                 &lt;=10 MHz 
               
               
                 ESD Protection 
                 &gt;2 Kv 
               
               
                 Supply Voltage 
                 5.0 +0.4 v/−0.5 v 
               
               
                 Voltage Regulator 
                 3.3 V 
               
               
                 Maximum Data Rate 
                 10 Mbits/s, 1 MBytes/sec (eight bit mode) 
               
               
                 Operating Temperature 
                 −40 C. to +85 C. 
               
               
                 Storage Temperature 
                 −40 C. to +125 C. 
               
               
                 Data Stream Error Detection 
                 Parity Byte 
               
               
                 Communication Format 
                 up to 10 MBit/Sec - SPI Master/Slave 
               
               
                 Pixel Data Format 
                 selectable - 10 bit, 8-bit compressed or 
               
               
                   
                 truncated 
               
               
                   
               
             
          
         
       
     
     Table 2 contains a description for the acronyms shown near various imager connections in  FIG. 7   b . 
     
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 SECTION 
                 NAME 
                 SIG TYPE 
                 DESCRIPTION 
                 DIR 
                 PAD # 
               
               
                   
               
             
             
               
                 Oscillator 
                 OSC1 
                 Crystal Osc 
                 Master Clock or cystal pin 1 
                 In 
                 16 
               
               
                   
                 OSC2 
                   
                 crystal oscillator pin 2 
                 Out 
                 17 
               
               
                 LVDS I/O 
                 VAA_LVDS 
                 Power 
                 3.3 V power supply for LVDS 
                 In 
                  8 
               
               
                   
                 VSS_LVDS 
                 GND 
                 Ground for LVDS 
                 In 
                 13 
               
               
                   
                 MOSI 
                 LVDS 
                 Serial Data In/Out (Differential) 
                 I/O 
                  9, 10 
               
               
                   
                   
                   
                 Note that the MOSI_b signal is 
               
               
                   
                   
                   
                 the positive signal with the 
               
               
                   
                   
                   
                 MOSI signal is the inverted 
               
               
                   
                   
                   
                 level. 
               
               
                   
                 SPSCLK 
                 LVDS 
                 Serial Data Clock (Differential) 
                 I/O 
                 11, 12 
               
               
                   
                   
                   
                 Note that the SPSCLK_b signal 
               
               
                   
                   
                   
                 is the positive signal with the 
               
               
                   
                   
                   
                 SPSCLK signal is the inverted 
               
               
                   
                   
                   
                 level. 
               
               
                 Control 
                 NSS 
                 CMOS 
                 Data transfer direction bit 
                 In 
                 18 
               
               
                 Test 
                 MISO/ 
                 CMOS 
                 Output signal for testing or 
                 Out 
                 19 
               
               
                   
                 MSC_OUT 
                   
                 illumination control. Can be set 
               
               
                   
                   
                   
                 steady state, to toggle during 
               
               
                   
                   
                   
                 integration, or output residual 
               
               
                   
                   
                   
                 data. 
               
               
                   
                 VAA_PIX 
                 Power 
                 Analog input to ADC in test 
                 In 
                 22 
               
               
                   
                   
                   
                 mode. When not used for 
               
               
                   
                   
                   
                 testing, this pin must be 
               
               
                   
                   
                   
                 connected to 3.3 V. 
               
               
                 Regulator 
                 Vreg_5 V 
                 Power 
                   5 V input supply for regulator 
                 In 
                  2 
               
               
                   
                 VAA_5 V 
                 Power 
                   5 V input supply for analog 3.3 V 
                 In 
                  7 
               
               
                   
                   
                   
                 supply 
               
               
                   
                 VDD_5 V 
                 Power 
                 5 V input supply for digital 3.3 V 
                 In 
                  5 
               
               
                   
                   
                   
                 supply 
               
               
                   
                 GND_5 V 
                 GND 
                 Ground for 5 V regulator supply 
                 In 
                  3 
               
               
                   
                 VDD_3.3_O 
                 Power 
                 Digital regulated 3.3 V supply 
                 Out 
                  4 
               
               
                   
                   
                   
                 output 
               
               
                   
                 VAA_3.3_O 
                 Power 
                 Analog regulated 3.3 V supply 
                 Out 
                  6 
               
               
                   
                   
                   
                 output 
               
               
                   
                 VG 
                 Analog 
                 Voltage regulator bias 
                 Out 
                  1 
               
               
                   
                   
                   
                 voltage out for decoupling. 
               
               
                   
                   
                   
                 Requires a cap to ground. 
               
               
                 Power 
                 VDD_3.3_I 
                 Power 
                 Digital regulated 3.3 V supply 
                 In 
                 14 
               
               
                   
                   
                   
                 input 
               
               
                   
                 GND 
                 GND 
                 Ground for VDD_3.3 
                 In 
                 15 
               
               
                   
                 VAA_3.3_I 
                 Power 
                 Analog regulated 3.3 V supply 
                 In 
                 21 
               
               
                   
                   
                   
                 input 
               
               
                   
                 VSS 
                 GND 
                 Ground for VAA_3.3 
                 In 
                 20 
               
               
                   
               
             
          
         
       
     
     Table 3 provides detail of various imager electrical power connections. 
     
       
         
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
             
             
               
                 Regulator 
                 The following signals must be connected to a 
               
               
                   
                 4.5 to 5.4 volt supply to 
               
               
                 Power: 
                 operate the chip: VREG_5 V, VDD_5 V (when 
               
               
                   
                 using VDD_3.3_O), and 
               
               
                   
                 VAA_5 V (when using VAA_3.3_O). 
               
               
                   
                 The corresponding ground is GND_5 V. 
               
               
                   
                 The Pin VG must be connected to a TBD capacitor for the 
               
               
                   
                 charge pump to operate properly. 
               
               
                 LVDS 
                 The signals VAA_LVDS must be connected to 
               
               
                 Power: 
                 a 3.3 ± TBD volt supply to operate the chip. 
               
               
                   
                 The signal VSS_LVDS is the LVDS ground. 
               
               
                 Analog 
                 The signals VAA_3.3_I must be connected to the 
               
               
                 Power: 
                 VAA_3.3_O or other 3.3 ± TBD volt supply to 
               
               
                   
                 operate the chip. The signal VSS_3.3 is the analog ground. 
               
               
                 Digital 
                 The signals VDD_3.3_I must be connected to 
               
               
                 Power: 
                 the VDD_3.3_O or other 3.3 ± TBD volt supply to operate 
               
               
                   
                 the chip. The signal GND is the digital ground. 
               
               
                 Pixel 
                 The signals VAA_PIX must be connected to 
               
               
                 Power 
                 the VAA_3.3_O or other 3.3 ± TBD volt supply to operate 
               
               
                   
                 the chip when not in ADC test Mode (See below). 
               
               
                   
               
             
          
         
       
     
     Table 4 provides detail of various imager operational connections. 
     
       
         
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
             
             
               
                 NSS: 
                 Serial data direction input. 0 = write to sensor, 
               
               
                   
                 1 = read from sensor. The NSS signal needs to be 
               
               
                   
                 asserted low for at least 6 oscillator cycles (0.6 μ seconds 
               
               
                   
                 with a 10 MHz clock) before starting the command 
               
               
                   
                 transmission. NSS must be held low for at least 
               
               
                   
                 10 oscillator cycles (1 μ second at 10 MHz) after 
               
               
                   
                 transmission completes. 
               
               
                 SPSCLK 
                 Bi-directional LVDS serial clock (direction determined 
               
               
                   
                 by NSS), where data is clocked (valid) on rising edge for 
               
               
                   
                 input and output. The SPSCLK signal must be set high 
               
               
                   
                 before each transition of NSS and must remain high for 
               
               
                   
                 at least 6 camera oscillator cycles after the 
               
               
                   
                 transition. (0.6 μ seconds at 10 MHz). 
               
               
                 MSC_OUT 
                 Miscellaneous output pin. Can be toggled during 
               
               
                   
                 integration time or 
               
               
                 (MISO): 
                 set to a specified level, also can send the residual registers 
               
               
                   
                 from a previous image while sending an image command. 
               
               
                   
                 Refer to the command bits tst, oba, and obb in byte 0 
               
               
                   
                 of the command string. 
               
               
                 MOSI: 
                 Bi-directional LVDS serial data (directed determined 
               
               
                   
                 by NSS). Data is sent most significant bit first. 
               
               
                   
               
             
          
         
       
     
     Table 5 provides detail of various imager test connections. 
     
       
         
               
               
             
           
               
                 TABLE 5  
               
               
                   
               
             
             
               
                 VAA_PIX: 
                 This pin can be used to input a voltage directly into the 
               
               
                   
                 ADC during testing when ADCtest (bit 5 of byte 3) of the 
               
               
                   
                 command sequence is set. When this bit is not set this pin 
               
               
                   
                 must be connected to 3.3 volts. 
               
               
                   
               
             
          
         
       
     
     The imager is controlled by an 18 byte serial command described herein with reference to Table 6. These commands are sent from the processor with the NSS line held low. The imager then gathers the requested image and sends the resulting pixel data followed by a parity byte. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Command Summary 
               
             
          
           
               
                 Name 
                 bit 7 
                 bit 6 
                 bit 5 
                 bit 4 
                 bit 3 
                 bit 2 
                 bit 1 
                 bit 0 
               
               
                   
               
               
                 Control 
                 tst 
                 ckbd 
                 tbo 
                 cbo 
                 obb 
                 oba 
                 rsh 
                 sfm 
               
             
          
           
               
                 idac_iadc_Id 
                 idac_iadc_Id 
               
             
          
           
               
                 idac_ibias_Id 
                 Unused 
                 idac_ibias_Id 
               
             
          
           
               
                 voffset_Id 
                 psfd 1 
                 psfd 0 
                 adctest 
                 Voffse_Idt 
               
             
          
           
               
                 Vreflo 
                 ffs 
                 irr 
                 iad 
                 cont 
                 Vreflo_Id 
               
             
          
           
               
                 Gain 1 
                 Gain 1 
               
               
                 Gain 2 
                 Gain2 
               
               
                 NumFrames 
                 Number of Frames (ones compliment/twos compliment if start 
               
               
                   
                 row = last row) 
               
               
                 NumIntegration Frames 
                 Number of Integration Frames (ones compliment) 
               
               
                 LastRow 
                 Last Row of Image 
               
               
                 StartRow 
                 Row Read Counter Start Value (Integration Rows = 
               
               
                   
                 LastRow − StartRow) 
               
               
                 FirstRow 
                 First Row of Image 
               
               
                 RowOffset 
                 Row Offset of Second Frame from First Frame 
               
               
                 LastColumn 
                 Last Column Scanned 
               
               
                 ResetColumn 
                 Column Read Counter StartValue (Int. Pixels = 
               
               
                   
                 LastColumn − ResetColumn) 
               
               
                 LastReadColumn 
                 Last Column of Image 
               
               
                 FirstColumn 
                 First Column of Image 
               
               
                 ColumnOffset 
                 Column Offset of Second Frame 
               
               
                   
               
             
          
         
       
     
     The imager can be operated with either an up to 10 MHz oscillator connected to OSC 1 , or an appropriate resonator circuit connected across OSC 1  and OSC 2  as shown in the Figs.  FIG. 7   c  depicts the imager serial peripheral interface data timing.  FIG. 7   d  depicts the imager command and data sequence and timing. 
     With reference to Tables 7-11, each bit (bits  0 - 7 ) of each byte (bytes  0 - 17 ) of the 18 byte serial imager command set is described. Byte 0: Control Byte 
                                                 TABLE 7               bit 7   bit 6   bit 5   bit 4   bit 3   bit 2   bit 1   bit 0                   tst   ckbd   tbo   Cbo   Obb   oba   rsh   sfm                    
Description:
 
Used to set control bits for test modes, gain control pattern, output format, integration time, and dual frame mode.
 
     tst: Test. Causes the residue from the previous instruction to be sent on the spcl_pin_out as the current instruction is received. The residue contains the values of the command stream including the revised frame, row and column counters after an image is taken. 
     ckbd: “Checkerboard pattern.” Causes the pixel gain to be set to gain_ 1  when the exclusive or of the least significant bits of the pixel&#39;s row and column address is 0 and to gain_ 2  when it is 1. When ckbd is not set, gain_ 1  is used on the first frame and gain_ 2  on the second frame. (When sfm (second frame only) is set and ckbd is 0, gain_ 2  is used.) 
     tbo: Ten bit output mode—Causes all 10 bits of the a/d output to be sent, if cbo is also set, the high 8 bits are the compressed value. When tbo is not set, the high 8 bits, only, are transmitted. Note that each byte takes ten imager clock cycles and the data lines will always be set to bits  1  and  0  of the ADC value during the last two imager clock cycles of the byte transmission period, regardless of the tbo or cbo values. Only eight SPSCLK clock cycles will be sent in the eight bit modes, with the clock line idle for the last two bit times of a pixel. In 10 bit output mode, the 10 SPSCLK clock cycles will be issued per pixel. 
     cbo: Compressed bit output mode—causes the 10 bit to 8 bit log based compression to compress the ten bit a/d output into 8 bits which are transmitted on the high 8 bits of the output. 
     obb Output bit control “b”—Causes MSC_OUT pin (referred to as the MISO pin in some documentation) to switch to its compliment state during sensor integration periods and causes no response when it is not set. 
     oba: Output bit control “a”—sets the MSC_OUT pin (referred to as the MISO pin in some documentation) to default to 1 if it is 1 and to 0 otherwise. 
     rsh: Row Shift—Causes the number of integration rows in a dual frame mode to be reduced by one—to an odd number. This has the effect to move the integration time to the next lower row and to allow the integration time to be advanced by single row increments. Before, because of the dual row processing in the dual frame mode, the integration time could only be increased in double row increments and the partial row setting could only cover a major portion of one of those two rows leaving a one row time gap in the integration time setting capability. Rsh must be 0 when the integration time is less than 1 row (StartRow=LastRow) and when the sfm (second frame only) is set. 
     sfm: Single frame mode—sets the mode to single frame (second frame only). This results in a single integration frame with row offsets and gain_ 2  applied as for the second frame in dual frame mode. 
     Byte 1: idac_iadc_ld 
                                                 TABLE 8               bit 7   bit 6   bit 5   Bit 4   bit 3   bit 2   bit 1   bit 0                   iadc   iadc 6   iadc 5   iadc 4   iadc 3   iadc 2   iadc 1   iadc 0       7                    
Description:
 
     Current reference setting for the Imager ADC. Recommended default is 48 (0x30). 
     Byte  2 : idac_ibias_ld 
                                                 TABLE 9               bit 7   bit 6   bit 5   Bit 4   bit 3   bit 2   bit 1   bit 0                   un-   unused   Bias 5   Bias 4   Bias 3   Bias 2   Bias 1   Bias 0       used                    
Description:
 
     Current Bias setting for the ADC. Recommended default is 14 (0x0e). 
     Byte  3 : voffset_ld 
                                                 TABLE 10               bit 7   bit 6   bit 5   Bit 4   bit 3   bit 2   bit 1   bit 0                   psfd   psfd 0   adctest   offset 4   offset 3   offset 2   offset 1   offset 0       1                    
Description:
 
     pfsd  1 : Power supply frequency divider bit  1 . This enables quieting the power supply during critical row sampling operation. 
     ‘0’—normal 
     ‘1’—regulator clk stopped during row_enable (experimental) 
     pfsd  0 : Select frequency of power regulator charge pump. This should be set to provide least RF interference. The oscillator divisor should be set so that the charge pump operates at approximately 2.5 MHz. (Set this bit when using a 5 MHz resonator, clear it when using 10 MHz.) 
     ‘0’—main clock divided by 4 for regulator 
     ‘1’—main clock divided by 2 for regulator 
     adctest: Analog Digital Converter Test—Setting this bit causes the Pixel data to be replaced with the voltage input on VAA_PXL as the input to the input to the ADC for testing. 
     voffset: Voltage Offset—This is the Voltage Offset for the DAC. Recommended default is 16 (0x10). Scaling for this value is 4 mV/bit, with a value of 16 corresponding to 0V. 
     Byte  4 : Frame Control, Vreflo 
                                                 TABLE 11               bit 7   bit 6   bit 5   Bit 4   bit 3   Bit 2   bit 1   bit 0                   ffs   irr   iad   cont   Vreflo 3   Vreflo 2   Vreflo 1   Vreflo 0                    
Description:
 
     ffs: First frame single—causes 0 additional integration frames to be added on the first frame, the number of added integration frames set minus one on the second frame, and the full number of added integration frames set for all frames after the first two 
     irr: image row reset—causes the frame to be reset without reading, essentially starting a long integration. 
     iad: image A/D—causes the frame to be read without resetting first, ending a long integration. 
     cont Continuous—Continuously take images and send data. 
     Vreflo Voltage Reference Low—ADC Low Voltage Reference—recommended default is 6. 
     Byte  5 : Gain_ 1   
     This gain is for the first half of an image or the even pixels of a checkerboard image. Gains are scaled as ⅛ of an F-Stop per bit. (8=gain of 1) 
     Byte  6 : Gain  2   
     This gain is for the second half of an image or the odd pixels of a checkerboard image. Gains are scaled at ⅛ of an F-Stop per bit. This gain is used in Single Frame Mode. 
     Byte  7 : NumFrames 
     The binary or ones compliment of the number of requested image frames. 
     Notes: 
     This is a ones complement number so to read a single frame set F to 254 since the actual number of frames will be [255−NumFrames]. However, if the integration time is less than a row then NumFrames must be set to 255 for a single frame, 256−{desired number of frames} in the general case. 
     Byte  8 : NumIntegrationFrames 
     The binary or ones compliment of the number of integration frames. The row/column counters are used to determine integration time as well as actual read/reset position. The integration frame counter allows additional full frames to be added to the integration time. 
     Notes: 
     This is a ones compliment number so to integrate over a single frame set NumIntegrationFrames to 254 since the actual number of integration frames will be 255−NumIntegrationFrames. 
     Byte  9 : LastRow 
     Last row of first image window in absolute coordinates. Valid values are from 0 to 183. The number of rows in each image will be equal to [LastRow−FirstRow+1]. 
     Byte  10 : StartRow 
     Starting row count of read row in absolute coordinates. The implementation is such that there is both a read row and reset row counter. Once set, these counters stay separated by the specified amount since they are incremented in unison. The reset row always starts at row  0 . Specifying a small number for SR and large number for LR would mean a large delta between reset and read and hence larger integration times. Valid values are from 0 to 183. 
     Notes: 
     StartRow=LastRow—{integration rows}. If StartRow=LastRow, then integration becomes pixel times only. Note also that in this case the NumFrames value must be adjusted. The value of StartRow must be greater than or equal to FirstRow, discussed next. When the rsh (row shift) bit is set the StartRow must be less than the LastRow. 
     Byte  11 : FirstRow 
     First row of first window in absolute coordinates. Valid values are from 0 to 183. 
     Notes: 
     The value of FirstRow must be less than or equal to the value of LastRow. 
     Byte  12 : RowOffset 
     Second window row offset relative to coordinates of first window. The first row to be read in the second window is determined by the sum of FirstRow and RowOffset. 
     Notes: 
     The value of RowOffset must be greater than the value of [LastRow−FirstRow] (may not overlap). The value of RowOffset must also be less than [184−LastRow] (Must fit on imager). This offset is also applied in single frame mode (sfm=1 in byte  0 ) 
     Byte  13 : LastColumn 
     Last column of first window that is sequenced through in absolute coordinates. Note that this could be different than LastReadColumn. Valid values are from 0 to 255. 
     Notes: 
     If LastColumn is greater than LastReadColumn, then this will establish the time between rows. Best results are obtained by keeping LastColumn as close as possible to LastReadColumn. This value must be greater than LastReadColumn and it must be at least 3 greater than ResetColumn. LastColumn should typically be LastReadColumn+1. 
     Byte  14 : ResetColumn 
     Reset column in absolute coordinates. This value establishes the sub row integration time of the image. ResetColumn=LastColumn—{integration pixel times} Valid values are from 0 to 252. 
     Notes: 
     The value of ResetColumn must be at least three less than LastColumn since reset occurs on ResetColumn+2. 
     Byte  15 : LastReadColumn 
     Last read column of first window in absolute coordinates. This value sets the last column to actually read. This could be different than the last column cycled through. Valid values are from 1 to 254. 
     Notes: 
     The value of LastReadColumn must be greater than FirstColumn. See section 6.0 Known Issues about column data offset, which requires this value to be set one higher than otherwise expected. 
     Byte  16 : FirstColumn 
     First column of first window in absolute coordinates. The column is both sequenced through and read. Valid values are from 0 to 252. 
     Notes: 
     The value of FirstColumn must be less than or equal to LastReadColumn. 
     Byte  17 : ColumnOffset 
     Second window column offset relative to coordinates of first window. The first column to be read in the second window is determined by the sum of FirstColumn and ColumnOffset. Valid values are from 0 to 255. 
     Notes: 
     The offset is applied only when reading one frame, when SFM=0 (byte  0 ). 
     The exposure time is defined as the time from the reset of a pixel until the time that pixel is read out. To establish a desired exposure time for each pixel two sets of counters are used: one for resetting (starting exposure) and one for reading (ending exposure). Each set of counters contains a frame counter, and row counter, and a pixel (or column) counter. The pixel counter is incremented each pixel time (10 clock cycles) unless it is equal to the LastColumn value in which case it is set to the FirstColumn value. At this rollover point, the row counter gets incremented. If the row counter would increment past the LastRow value, it is set to the FirstRow value. The frame counter is incremented when the row counter equals the LastRow value. When it reaches zero the scan (either reset or read) is completed. 
     The sets are initialized differently: The reset counters getting set to 0xFF, FirstRow, First Column for the frame, row, and pixel counters. The read counters are set to the NumIntegrationFrames, StartRow, and ResetColumn respectively. Additional counters and logic handle the dual frame, row shift, multiple images, and other variations. As the read counters point to a pixel while the frame counter equals 0xFF, the data is transmitted to the host. Once all of the data is sent, the parity byte is sent. 
     The finest granularity of exposure time is the PixelTime. One PixelTime is one-tenth of the crystal frequency. 8 data bits+2 bits spacing. Every exposure setting has at least 2 PixelTime resulting in a 2 PixelTime step whenever crossing integration boundaries (ex. sub row time to row time). The following are the equations that govern the integration times for the single window mode.
     #cols=LastReadColumn−FirstColumn+1   #rows=LastRow−FirstRow+1   intpix=LastColumn−ResetColumn   introw=LastRow−StartRowCount   intframe=255−NumIntFrames   PixelTime=Clock Period*10 (1 μs @ 10 MHz, 2 μs @ 5 MHz)   RowTime=#cols+(LastColumn−LastReadColumn+4)   FrameTime=#rows*Rowtime   Exposure=PixelTime*[intpix+(RowTime*introw)+(Frametime*intframe)]   In the dual window mode (when either RowOffset (byte  12 ), or ColumnOffset (byte  17 ) are non-zero), the following are the equations that govern the integration times.   #cols=LastReadColumn−FirstColumn+1   #rows=2*(LastRow−FirstRow+1)   intpix=LastColumn−ResetColumn   introw=2*(LastRow−StartRowCount)−rsh   intframe=255−NumIntFrames   PixelTime=Clock Period*10 (1 μs @ 10 MHz, 2 μs @ 5 MHz)   RowTime=#cols+(LastColumn−LastReadColumn+4)   FrameTime=#rows*Rowtime   Exposure=PixelTime*[intpix+(RowTime*introw)+(Frametime*intframe)]   

     The sampling of a row of pixels takes place in four added pixel times beginning during the last scanned pixel time for the preceding row and extending for three more unaccounted for pixel times. Then there is one additional unaccounted for pixel time before the first pixel time during which the first pixel of the row is read into a pipeline a/d which takes 8 pixel times to present the finished reading. This is where the +4 in the above calculation of row time comes from. The last read column must be at least one less than the last scanned column. This may be increased to at least eight less than the last scanned column to assure that partially finished results are not sitting in the pipeline a/d during the four pixel read row period while the pipeline a/d is shut down. The row requires a processing time equal to the number of the last scanned column minus the number of the first scanned column+5. The reset processing requires two additional reset processing periods after the assigned reset column, the implication being that the pixel reset column must be at least three less than the last scanned column. The reset row periods do not interfere with the normal integration period or the read pixel operation which may be in progress. Due to the row sampling method used, the actual effective integration period extends approximately from the time the row is reset to the time of the first pixel of the row in which row is read. 
     A temperature reading can be obtained by reading the four columns 0 through 3. A difference between the second and fourth columns values (converted to 10 bits) multiplied by 0.367 and added to 113 yields the temperature in degrees Celsius. These values assume a gain of one and default or standard analog settings. In practice, many rows should be averaged together to more accurately derive temperature. 
     After transmitting the image data requested, a parity byte will be transmitted. This byte is the result of “Exclusive OR” of all of the data sent as part of the image with 30 (0x1E). 
     Turning now to  FIGS. 8   a  through  8   c , an embodiment of an enhanced transceiver  809   a ,  809   b ,  809   c  is described with interconnection between an imager board  835   a  and a processor  808   a . The chip is depicted as comprising: a processor interface logic block  865   a ; a first read address  866   a ; a second read address  867   a ; a 32,768 byte, 8-bit wide, dual port memory  868   a ; an incoming data logic block  869   a  having a write address; an LVDS transceiver  870   a ; a NSS connection  871   a ,  871   b ,  871   c ; a MOSI connection  872   a ,  872   b ,  872   c ; a NCMND connection  873   a ,  873   b ,  873   c ; a SPSCLK connection  874   a ,  874   b ,  874   c ; a MISO connection  875   a ,  875   b ,  875   c ; a READY connection  876   a ,  876   b ,  876   c ; a NRESET connection  877   a ,  877   b ,  877   c ; a SNSS connection  879   a ,  879   b ,  879   c ; a DATA+ connection  880   a ,  880   b ,  880   c ; a DATA− connection  881   a ,  881   b ,  881   c ; a DCLK+ connection  882   a ,  882   b ,  882   c ; a DCLK− connection  883   a ,  883   b ,  883   c ; a LVDS direction line  884   a ; a LVDS source select line  885   a ; a serial command data line  886   a ; a serial command clock line  887   a ; control signals  888   a ; register data  889   a ; an Imosi line  890   a ; an Ispclk line  891   a ; a 2.5 VDC connection  892   b ,  892   c ; a GND connection  893   b ,  893   c ; a V AA     —   LVDS connection  894   c  and a V SS     —   LVDS connection  895   c . It should be understood that the SNSS connection  879   a ,  879   b ,  879   c  may not route through the enhanced transceiver, rather the SNSS connection is directly from a processor to an imager. In a preferred embodiment, the enhanced transceiver is configured to function somewhere between a truly random access memory and a first-in-first-out (FIFO) memory. For example, in a first frame single mode the enhanced transceiver provides the ability to create a synthetic high dynamic range image effect by making at least a portion of a first image and at least a portion of a second image available to a processor. Preferably, the imager only needs to receive one command instruction to transmit the two images. It should be understood that an enhanced transceiver and, or, imager may be configured to provide access to more than two different images. These features are useful when the associated vision system comprises algorithms that utilize pixels from more than one image such as in moisture detection systems that acquire at least one image without supplemental illumination and one with supplemental illumination. Exterior light control systems that acquire at least one image at a first integration period and at least one image at a second integration period. The successive images are acquired very close in time when no intervening command instruction is required. It should also be understood that a processor may be integrated along with the LVDS and memory of the enhance transceiver. Alternatively, image pre-processing features may be incorporated into the enhanced transceiver. For example, the enhanced transceiver may create a synthetic high dynamic range image, it may provide light source extraction functions, it may provide light source classification functions, subcombination thereof or combinations thereof. It is within the scope of the present invention to provide at least one imager, at least one enhanced transceiver, at least one processor, a subcombination thereof or combination thereof on a common board and, or, silicon wafer. 
     The following example describes a preferred embodiment of an enhanced transceiver. 
     EXAMPLE ENHANCED TRANSCEIVER 
     The ENHANCED TRANSCEIVER serves as a bi-directional Low Voltage Differential Signal (LVDS) transceiver for serial clock (SPSCLK) and data (MOSI) signals. The chip provides 32768 bytes of memory to buffer image data sent from the image sensor after image acquisition and to allow the processor to read this image data asynchronously. The chip provides a 5V tolerant interface with the processor. The chip provides memory access functions that facilitate dual image processing, result storage, and memory testing as described herein. The chip provides a parity calculation to verify proper transmission from an imager. 
     Table 12 depicts the enhanced transceiver operating modes along with status of related chip connections. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 12 
               
             
             
               
                   
               
               
                 Operating Modes 
               
             
          
           
               
                 Mode 
                 NSS 
                 NCMND 
                 Loop Back 
                 MOSI 
                 MISO 
                 DCLK and DDATA 
                 SNSS 
               
               
                   
               
               
                 Imager 
                 L 
                 H 
                 — 
                 To LVDS to 
                 Inactive 
                 From MOSI to Imager 
                 L 
               
               
                 Instruction 
                   
                   
                   
                 Imager 
               
               
                 Image 
                 H 
                 H 
                 0 
                 Inactive 
                 Read From 
                 From Imager To Memory 
                 H 
               
               
                 Reception 
                   
                   
                   
                   
                 Memory 
               
               
                 Loop back 
                 H 
                 H 
                 1 
                 To Memory 
                 Read From 
                 High Impedance 
                 H 
               
               
                 Mode 
                   
                   
                   
                   
                 Memory 
               
               
                 Status 
                 H 
                 L 
                 — 
                 Inactive 
                 Register 
                 From Imager to Memory 
                 H 
               
               
                   
                   
                   
                   
                   
                 contents 
               
               
                 Command 
                 L 
                 L 
                 — 
                 To Registers 
                 Inactive 
                 High Impedance 
                 H 
               
               
                   
                   
                   
                   
                 then 
               
               
                   
                   
                   
                   
                 Memory 
               
               
                   
               
             
          
         
       
     
     When transitioning between modes the lines should be switched in sequence to prevent accidentally entering Imager Instruction mode which will cause unwanted interference from the imager. 
     At the start of every image acquisition cycle, an 18 byte control instruction is sent from a processor to the imager. It should be understood that the enhanced transceiver is capable of transmitting other length control instructions, the imager of the example contained herein happens to utilize an 18 byte control instruction. The NSS (Not Slave Select) line is set low and the NCMND (Not Command) line is set high during this transmission. In this mode, the enhanced transceiver should serve only to convert the signals from the microcontroller to LVDS for transmission to the imager. The LVDS transceiver should be set to output data. The MOSI signal from the microcontroller is output on the DDATA+/DDATAI− LVDS pair. The SPSCLK from the microcontroller is output on the DCLK+/DCLK− pair. The imagers NSS line should be driven low in this mode. After the integration cycle is complete, the imager will transmit the acquired image over the MOSI &amp; SPSCLK differential pairs to the enhanced transceiver. When NSS is high the LVDS transceiver is set to input data. The incoming data logic block should serve to receive the incoming serial data stream and store each byte to memory, incrementing the write memory location with each byte. See also the description of Loopback mode below. The processor is responsible for managing image requests and memory usage. Overflow conditions will cause loss of data. 
     When the loop back control bit is set and NSS and NCMND lines are high the serial data stream is sourced from the MOSI and SPSCLK lines from the processor rather than the LVDS transceiver. 
     The processor will read data from the enhanced transceiver memory asynchronously from data reception. The NSS and NCMND lines are set high in this mode. Data is read in a first-in-first-out (FIFO) order. The processor can monitor the READY signal to determine if there is data available. Note that the state of the ready line does not affect the operation of the reading. Independence from the ready logic permits using the memory as general purpose serial RAM with auto-incrementing pointers without regard to the ready logic. The processor receives the data by clocking the SPSCLK line, which clocks the data out serially on the MISO line. When the loop back control bit is set the data on the MOSI line is stored into the memory simultaneously using the same clock edges. Command bits can also be used to select which of two read pointers are used to access data. 
     When the NSS and NCMND lines are both low, the data sent from the processor is stored into a command register, the read and write pointer registers, and into memory. Details of the various command bits and command sequences are provided later in this document. No clock or data signals are sent out the LVDS lines in this mode, the LVDS lines are actively held idle (high) by the imager during this state. 
     When the NSS is high and NCMND line is low, the parity test bit and write pointer is latched and shifted out to the processor using the SPSCLK and MISO lines. Additional reads will transfer the values of Read Pointer  1 , Read Pointer  2 , command register, and parity register. The reception of data from the imager is not affected in this state. This combination should not be needed when the loop back bit is set. Requesting status in Loop Back mode is not defined. 
     A reset line is provided as an input to the enhanced transceiver. When reset is set low, the chip is set to an “empty” state (Write pointer to 7FFF hexadecimal, read pointers to 0. All internal registers and memory pointer counters should be initialized. Read Pointer  1  will be selected. 
     While operating in Image Reception and Status Modes, the Ready line will be set high when new data is written into the memory. It will be cleared when the last byte written is read by the processor. It also will be cleared when setting the alternate bit in the command register. When operating in the alternate read modes, care should be taken to set the read pointers so that the write pointer will not be incremented past a read pointer if the ready line is set. 
     When the Alternate bit is set in the command register, the data output during reading alternates which read pointer is used to read the memory. If the first byte if read using read pointer  1 , the next byte will be read using pointer  2  and so on. This mode permits simultaneous processing of two images. 
     When the first byte of an imager command is sent, the parity register is set to 14 (0xe). Each byte received during Image Reception mode is then exclusive-ORed with the Parity Register. When the chip is set to Status mode, the first bit transmitted (MSB of the Write Pointer) will be set to one if the parity register is equal to zero. 
     The maximum instruction data clock rate is 10 MHz. The maximum image data reception clock rate is 10 MHz (1 μs/byte). The maximum processor data read clock rate is a function of the interconnection transmission capability, preferably greater than 12 MHz. 
     All data is sent most significant bit first. All data is clocked on the rising edge of the appropriate clock. MISO and MOSI data are clocked by the SPSCLK signal, while the LVDS DATA lines are clocked using the DCLK lines. All data is processed in bytes. Reception of partial bytes must be avoided. Pointer register values are transferred as two bytes with the first bit being don&#39;t care followed by the fifteen bit value, most significant bit first. The exception to this is the use of the first bit of the write pointer for the parity check function. 
     The enhanced transceiver may be configured to operate from a single 2.5 VDC supply.  FIGS. 8   d  and  8   e  depict the associated processor signal waveforms and LVDS signal waveforms, respectively. The first byte received from the microcontroller after entering command mode is the command byte. If required, a value for the pointer register is received in the next two bytes. Any additional bytes sent while command mode is selected will be written to memory using the write pointer register. Tables 15 and 14 depict details of the associated enhanced transceiver command byte. 
     
       
         
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 13 
               
               
                   
               
               
                 bit 7 
                 bit 6 
                 bit 5 
                 bit 4 
                 bit 3 
                 bit 2 
                 bit 1 
                 bit 0 
               
               
                   
               
             
             
               
                 Loop 
                 Alternate 
                 Select 
                 Load reg. 
                 (spare) 
                 Write 
                 Read 
                 Read 
               
               
                 back 
                   
                 register 
                   
                   
                 register 
                 reg 2 
                 reg 1 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 14 
               
             
             
               
                   
               
               
                 Bit Descriptions 
               
             
          
           
               
                   
                 Bit 
                 Bit Name 
                 Description 
               
               
                   
                   
               
               
                   
                 0 (0x1) 
                 Read Reg. 1 
                 Indicates that the primary read 
               
               
                   
                   
                   
                 pointer will be loaded or selected. 
               
               
                   
                 1 (0x2) 
                 Read Reg. 2 
                 Indicates that the secondary read 
               
               
                   
                   
                   
                 pointer will be loaded or selected. 
               
               
                   
                 2 (0x4) 
                 Write Reg. 
                 Indicates that the write pointer will 
               
               
                   
                   
                   
                 be loaded. 
               
               
                   
                 3 (0x8) 
                 (not used) 
               
               
                   
                 4 (0x10) 
                 Load Reg. 
                 When set the address sent next will 
               
               
                   
                   
                   
                 be loaded into the selected 
               
               
                   
                   
                   
                 register(s). 
               
               
                   
                 5 (0x20) 
                 Select Reg. 
                 Setting this bit causes the read 
               
               
                   
                   
                   
                 register indicated to be selected for 
               
               
                   
                   
                   
                 reading in normal read mode. 
               
               
                   
                 6 (0x30) 
                 Alternate 
                 When set, the selection of which 
               
               
                   
                   
                 Mode 
                 pointer is used for reading alternates 
               
               
                   
                   
                   
                 with each data byte received 
               
               
                   
                 7 (0x40) 
                 Loop Back 
                 When set the microprocessor MISO 
               
               
                   
                   
                 Mode 
                 and SPSCLK lines will be used to 
               
               
                   
                   
                   
                 feed data into memory while 
               
               
                   
                   
                   
                 clocking data out in normal read 
               
               
                   
                   
                   
                 mode (NSS and NCMND high). 
               
               
                   
                   
               
             
          
         
       
     
     Table 15 depicts a series of example enhanced transceiver commands. 
                                       TABLE 15                   Example Commands            Command   Value   Parameters   Description               Insert Data, reset   0x00   (at least one   Raw data bytes are placed into FIFO as if       Loopback/Alternate       byte of Raw   they had come from an imager. Used for       modes       data)   data storage and testing. Clears loop                   back and alternate bits as well.       Set Read Pointer 1   0x11   2 bytes   Stores a new value in the first read pointer               Address       Set Read Pointer 2   0x12   2 bytes   Stores a new value in the second read               Address   pointer       Set Write Pointer   0x14   2 bytes   Stores a value into the write pointer               Address       Set Multiple Pointers   0x13,   2 bytes   Stores a value for multiple pointers, as           0x15,   Address   indicated by the least significant 3 bits.           0x16,       See note below for more information.           0x17       Select Read Pointer 1   0x21   none   Selects the default read pointer as active       Select Read Pointer 2   0x22   none   Selects the alternate read pointer as                   active       Set and Select 1   0x31   2 bytes   Sets and selects the default read pointer               Address       Set and Select 2   0x32   2 bytes   Sets and selects the alternate read pointer               Address       Set Alternate Mode 1   0x61,   0x61: none,   Set the active read pointer to alternate           0x71   0x71:   with each byte read, starting with the               Address   default pointer.       Set Alternate Mode 2   0x62,   0x62: none,   Set the active read pointer to alternate           0x72   0x72:   with each byte read, starting with the               Address   alternate pointer.       Loopback Data   0x80   (normally at   First Raw data bytes are placed into FIFO               least one   as if they had come from an imager.               byte of Raw   During subsequent normal data reads               data)   (NSS lines high) the MOSI data coming                   from the processor is written into the                   memory. This will provide a faster                   memory test or provide for processed                   image data to be stored while reading.                    
Typical usage examples.
 
     The following assume starting from a reset or empty pointer states: no loop back or alternate bits set, NReset, NSS, and NCMND bits High.
     1) Gather One Image from the imager
       a) Set NSS Low   b) Send Imager Commands   c) Set NSS High   d) Get Imager Data. Wait while READY low, read data when READY high.   
       2) Gather multiple images, normal reading:
       a) Set NSS Low   b) Send Imager Commands   c) Set NSS High   d) Get Imager Data. Wait while READY low, read data when READY high.   e) Periodically set the NCMND bit low at the expected time of completion of image data. Get the Write address and compare with the expected length.   f) Once the preceding image has completed transferring to the FIFO, steps a-c can be repeated to start another image. Care must be taken to not fill the memory to a point where the write pointer passes the read pointer. The registers will roll over, but there is a physical limit to the chip   
       3) Gather image (or two images from one command) processing two halves of the data together using the Alternate Mode
       a) Set the NCMD bit Low   b) Set NSS Low   c) Sent the Alternate Mode command byte indicating a load of read pointer 2  (0x52).   d) Calculate the Read Pointer  2  value from the known value of the Write Pointer. (ReadPtr 2 =WritePtr+1+Length of First part)   e) Send the Most significant byte of Read Pointer  2     f) Send the Least significant byte of Read Pointer  2     g) Set the NCMND line High.   h) Send Imager Commands   i) Set NSS High   j) Repeatedly set the NCMND bit low. Get the Write address and compare with the value set for Read Pointer  2 . Set NCMND High. Once the write pointer has advanced past Read Pointer  2  continue on to the next step.   k) Read data, monitoring the ready line for data availability. The first byte read will be the first byte received from the first image request. The second byte received will be accessed using Read Pointer  2 .   
       4) Gather two images processing them using the Alternate Mode
       a) Set NSS Low   b) Send Imager Commands   c) Set NSS High   d) Repeatedly set the NCMND bit low. Get the Write pointer value and compare with the expected length. Set NCMND High if not done.   e) Once the initial image has completed transferring to the FIFO, set NCMND Low.   f) Set NSS Low to enter command mode   g) Sent the Alternate Mode command byte indicating a load of read pointer  2  (0x52). This will set the READY line Low when returning to read mode.   h) Calculate the Read Pointer  2  value as one past the Write Pointer. (ReadPtr 2 =WritePtr+1)   i) Send the Most significant byte of Read Pointer  2     j) Send the Least significant byte of Read Pointer  2     k) Set the NCMND line High.   l) Send Imager Commands for second image.   m) Set NSS High.   n) Read data, monitoring the ready line for data availability. The first byte read will be the first byte received from the first image request. The second byte received will be the first byte of the second Image.   
       5) Use Loopback Mode to perform a memory test
       a) Set NSS and NCMND Low.   b) Send the Loopback mode command (0x80).   c) Send the first byte of the memory test. Additional bytes could be sent as well.   d) Set NSS and NCMND High.   e) Send the next test values while reading the previous test values until done.   f) Set NSS and NCMND Low.   g) Send the Normal mode command (0x00).   h) Set NSS and NCMND High.   i) Read the last byte to reset the Ready signal and pointers to the empty state.   
       6) Use Loopback and Alternate modes to process two images, storing an intermediate result on the chip. The maximum size images in this mode are 8191 if the original data needs to be retained and 10923 if the images can be overwritten by results.
       a) Set NSS Low   b) Send Imager Commands   c) Set NSS High   d) Repeatedly set the NCMND bit low. Get the Write pointer value and compare with the expected length. Set NCMND High if not done.   e) Once the initial image has completed transferring to the FIFO, set NCMND Low.   f) Set NSS Low to enter command mode   g) Sent the Alternate command byte indicating a load of read pointer  2  (0x52).   h) Calculate the Read Pointer  2  value as one past the Write Pointer. (ReadPtr 2 =WritePtr+1)   i) Send the Most significant byte of Read Pointer  2     j) Send the Least significant byte of Read Pointer  2     k) Set the NCMND line High.   l) Send Imager Commands for second image.   m) Set NSS High.   n) Wait for the second image to be complete by monitoring the Write Address.   o) Read the first pixel of data from each image.   p) Go to Command Mode (NCMND and NSS Low), send Alternate Loopback (0xC0). Set NSS and NCMND High.   q) Perform required operations on Pixel data, Prepare two bytes of results to output to Queue.   r) Read next two pixels of data while transmitting results calculated.   s) Continue until done reading data.   t) Go to Command Mode, Send Normal (0), Set NSS and NCMND bits high.   u) Note that the last two results could be put into the Queue if needed, but since these are likely to be the sum check, it is unlikely that these results are needed.
 
Continue to Read and process the result data.
   
       

     A first embodiment of a mother board/imager board interconnection is shown in  FIG. 9   a . An image sensor chip  901   a  communicates with a processor  902   a  over a common bi-directional synchronous serial bus. The bus contains three signals: NSS  903   a  (NOT Slave-Select), MOSI  904   a  (data Master-Out-Slave-In), and SPSCKL  905   a  (serial clock). The NSS signal is uni-directional and allows the microcontroller to indicate to the image sensor if it is a bus slave (high-impedance input for receiving data) or a master (transmitting data). The microcontroller can set NSS low and send instructions to the image sensor for image acquisition over the MOSI and SPSCLK lines. When NSS is set high, the image sensor executes image acquisition according to the instructions and returns the image data over the bus. The bus signals are typically operated at CMOS logic level for the power supply used, typically 5.0V or 3.3V. 
     Another embodiment of a mother board/imager board interconnection shown in  FIG. 9   b , utilizes bi-directional low-voltage-differential-signaling (LVDS) for communication between the image sensor  901   b  and the processor  902   b . With this method, digital signals MOSI  904   b  and SPSCLK  905   b  are converted to differential pairs  910   b  and  911   b  by LVDS transceiver blocks  906   b ,  907   b ,  908   b , and  909   b . LVDS signals provide several advantageous. First, the use of a differential pair substantially increases noise immunity and is far more tolerant to any ground reference difference between the imager and the microprocessor. Secondly, the lower voltage signals (about −0.3V to +0.3V) emit substantially less electromagnetic interference than 5.0V or 3.3V digital signals. 
     An exemplary LVDS transceiver block is shown in  FIG. 9   j . A Fairchild Semiconductor FIN1019 LVDS driver  901   j  is used. Data signal  904   j  may be either a MOSI signal or an SPSCLK signal. The NSS signal  903   j   1  indicates the direction of data transfer. D+ and D− signals form a differential pair  910   j   1 ,  910   j   2 . In the example shown in  FIG. 9   b , the polarity is set for the image-sensor side transceivers  906   b ,  907   b . Thus, when NSS is low, data reception is enabled. For the controller side transceivers  908   b  and  909   b  an opposite polarity signal is provided to driver&#39;s  901   j  DE and NRE inputs by the controller. In this and other embodiments, imager instruction and parameter data is communicated over the same bi-directional bus as the acquired digital image. 
     It is also possible to provide two unidirectional busses, one for providing instructions and parameters from the processor to the image sensor and a separate bus for transmitting image data from the image sensor to the processor. In this case, the instruction and parameter bus may not have the high data rate requirements of the image data bus and therefore may be implemented using a simple technique such as a UART. The image data bus may be a unidirectional high speed digital bus, such as an LVDS bus, or may even be an analog signal, such as the common NTSC video standard, which is then digitally sampled at the processor. 
       FIG. 9   c  illustrates an embodiment similar to that of  FIG. 9   b . However, in the  FIG. 9   c  embodiment the image sensor side LVDS transceivers are integrated into the imager  901   c  along with the other components of this device. This integration reduces the part count, component cost, and imager board area associated with the image sensor side LVDS transceivers  906   b ,  907   b . As shown, the processor  902   c  side LVDS transceivers  908   c ,  909   c  remain with respective data  910   c , clock  911   c  and NSS  903   c  interconnections. It should be understood that communication protocols such as a serial bus, LVDS serial bus, a parallel bus, a UART, optical fiber, SPI bus, IIC bus, CAN bus, J 1815  bus, LIN bus, MOST bus, USB, fire-wire, or even a wireless link (e.g. Bluetooth) may be used to transmit data from the imager to the processor, from the processor to the imager and two individual communications connections can be employed with one for imager-to-processor communication and a second for processor-to-imager communication. 
     There are several applications where multiple image sensors may be utilized. For example, automatic vehicle exterior light control and moisture sensing are both applications which can be performed utilizing image sensing and processing. However, the optical requirements of both features are substantially different. An exterior light control imaging system must be designed to image small light sources at a distance and provide some color discrimination. A moisture sensing imaging system typically images a surface of a windshield. To better image the surface of a windshield, it is advantageous to tilt the image sensor forward. Furthermore, it is advantageous to provide supplemental illumination for an image sensor (such as an LED) and optionally to limit the spectral sensitivity of the imaging system to the spectral band of the illuminator. Specifically, it is most advantageous to use an infrared (IR) LED which is not visible to the vehicle driver or passengers and limit the sensitivity of the imaging system to the IR spectrum. As a result, the preferred optical configurations of a moisture sensing imaging system are often incompatible with the preferred optical configurations of an exterior light control imaging system, at least through means which are economical for wide adaptation of both features. Other vehicle imaging features may also be combined with exterior light control, moisture sensing or they may be incorporated with each other. These features may include but are not limited to: adaptive cruise control, collision warning or avoidance, weather condition detection, lane departure warning, blind spot warning, night vision, and driver drowsiness detection. Some of these features may be combined with each other utilizing a single image sensor and some may be combined through the use of multiple image sensors. 
     Another useful application requiring multiple image sensors is stereoscopic imaging. A stereoscopic imaging system utilizes at least two image sensors spaced apart from each other. The parallax effect causes objects at different distances to be imaged with different displacements relative to each other onto each image sensor. Very distant objects will be imaged onto the same location on each sensor. This effect can be used to obtain an accurate measurement of the distance of an object. This stereoscopic principle can be used for moisture sensing as described in commonly assigned U.S. Pat. Nos. 5,923,027 and 6,617,564 and U.S. patent application Ser. No. 09/970,728, the disclosures of which are incorporated in their entireties herein by reference, exterior light control, or any of the previously mentioned applications. 
       FIG. 9   d  illustrates an embodiment of the present invention which provides a highly economic means of providing a vision system including two or more image sensors. Two image sensors  901   d   1 ,  901   d   2  are provided on printed circuit board  950   d . Components common to both image sensors such as power supply  921   d  and oscillator  920   d  may be shared to reduce cost. Image sensors  901   d   1 ,  901   d   2  share a common bus for communication with a processor  902   d  which comprises signals MOSI  904   d  and SPSCLK  905   d . Each image sensor is preferably provided with its own enable/direction signal NSS  903   d   1 ,  903   d   2 . 
     Operation proceeds as follows: In order to acquire an image from image sensor  901   d   1 , image sensor  901   d   2  output is disabled and placed in a tri-state input mode by setting NSS- 2   903   d   2  low. Instructions are loaded into image sensor  901   d   1  from the microcontroller by setting NSS- 1   903   d   1  low while communicating instructions to image sensor  901   d   1  over MOSI  904   d  and SPSCLK  905   d  signals. After instructions are loaded, NSS- 1   903   d   1  is set high allowing the acquisition process to begin and enabling output from image sensor  901   d   1 . During this entire period NSS- 2   903   d   2  remains low. When acquisition from image sensor  901   d   1  is complete additional images may be acquired from image sensor  901   d   1  or images may be acquired from image sensor  901   d   2 . 
     To acquire images from image sensor  901   d   2  signal NSS- 1   903   d   1  is set low disabling output from image sensor  901   d   1 . Next, NSS- 2   903   d   2  is set high and then low to reset the image sensor and enable instruction loading. Image instructions are then communicated to image sensor  901   d   2  over signals MOSI  904   d  and SPSCLK  905   d . NSS- 2   903   d   2  is then set high enabling acquisition and readout of the image from image sensor  901   d   2 . During the entire process of acquiring images from image sensor  901   d   2 , NSS- 1   903   d   1  remains low. 
     The above process may continue indefinitely and in any order. Image acquisition may alternate between imagers or each imager may take multiple images sequentially. The use of each imager may depend upon the activation of features for which each imager is configured. Also, any number of image sensors may be provided on the common bus by adding the corresponding number of NSS lines. 
     The present invention may also be implemented with a variety of bus schemes. For example a parallel bus may replace the serial bus. The bus may also be an radio frequency interconnection, a light ray interconnection, or a fiber optic interconnection rather than a hardwired interconnection. The present invention comprises a shared bus for communication between one or more image sensors and one or more processors and means for selecting an image sensor. The means for selecting an image sensor may be through discrete signals, such as signals NSS- 1  and NSS- 2 , through an address bus, or through an address or identifier sent over the data communication bus. The later example may be implemented for example by sending and identifier /command instruction over the bus. An identifier allows each imager to determine if it should respond to the following command. The command may be an image acquisition instruction or a “go-to-sleep” instruction. A “go-to-sleep” instruction would allow the disabling of the image sensor(s) not acquiring images to prevent any bus interference with the active sensor. Non active image sensors would become active when an acquisition instruction is issued for the sensors address. Image sensor addresses may be set in hardware through digital inputs which are wired either high or low to set the address. This way each image sensor may be given a unique address. 
     While the embodiment of  FIG. 9   d  shows image sensors  901   d   1  and  902   d   2  co-located on a single circuit board, the present invention can also be implemented with image sensors located on different circuit boards or even in different general locations on, or in, a vehicle. In these cases, it may not be convenient to share some components such as voltage regulator  921   e  and oscillator  920   e , however the use of a common bus still provides economic advantage. When combining a moisture sensor with another function it may be necessary to incline the moisture sensor imaging plane while leaving the other imaging sensor such that the imaging plane is perpendicular to plane of the road. Several methods will facilitate this. The moisture sensor imager may be provided on a separate circuit board connected to the other circuit board through wires or flex circuit. The moisture sensor may be provided on a break-away section of the circuit board. Such a configuration would allow the image sensor sub-assembly to be manufactured on a flat circuit board and then the portion of the board containing the moisture sensor imager can be broken off and bent at the appropriate angle. Electrical connection may be maintained through wire jumpers. Finally, the image sensor sub-assembly may be manufactured on a flexible circuit board allowing the two image planes to be different. 
     The embodiment of  FIG. 9   f  is similar to that of  FIG. 9   d  except that signals MOSI  904   e  and SPSCLK  905   e  from processor  902   e  are converted to differential pairs  910   e ,  911   e  as described before in reference to  FIGS. 9   b  and  9   c  using LVDSs  908   c ,  909   c , respectively. The embodiment shown in  FIG. 9   e  is drawn such that each image sensor contains a LDVS transceiver, however external transceivers can also be used. In this case, the transceivers may be shared by the image sensors. 
     The embodiment of  FIG. 9   f  illustrates a multiple processor solution. In this embodiment, a second processor  930   f  communicates with one or more image sensors  901   f   1 ,  901   f   2  and performs some or all of the image processing associated with these sensors. Processor  930   f  communicates with main processor  902   f  which may be located remote from imager board. The data communicated may be entire images, a subset of the images, compressed images, the results of pre-processed images, or a decision on an action to take based upon processing of at least one image. Main processor  902   f  may communicate to second processor  930   f  various information such as parameters for processing, activation of various features, and vehicle status information. Main processor may perform a portion of the image analysis, or may make a control decision based upon information communicated from second processor  930   f . The main processor  902   f  may also perform communication with the vehicle either through discrete wiring or through a bus such as the CAN bus. Main processor  902   f  may also perform other functions such as control of an electro-optic mirror. It is also contemplated that main processor  902   f  may be a central processor, such as a “body controller”, which is typically responsible for multiple vehicle equipment functions. In this way second processor  930   f  can be responsible for the computation and data intensive image analysis tasks and main processor  902   f  may determine and execute a final control decision based upon the results of processing from  930   f  and possibly other vehicle information. Voltage regulator  924   f  and oscillator  920   f  may be provided. 
     Communication between main processor  902   f  and second processor  930   f  may be through a variety of means. Since the entire raw image data is not necessarily transmitted from second processor  930   f  to main processor  902   f  this communication link may be more flexible and of potentially lower bandwidth than the communication links between the imager and the processor. Example communication links include: a serial bus, LVDS serial bus, a parallel bus, a UART, optical fiber, SPI bus, IIC bus, CAN bus, J 1815  bus, LIN bus, MOST bus, USB, fire-wire, or even a wireless link (e.g. Bluetooth). 
     Second processor may be a microcontroller, digital signal processor (DSP), field-programmable gate array (FPGA), complex programmable logic array (CPLD), application specific integrated circuit (ASIC), or the like. It is also possible to integrate second processor  930   f  with one or more image sensors  901   f   1 ,  901   f   2 . In a preferred embodiment second processor is implemented with an FPGA such as a Cyclone™ series FPGA available from Altera Corporation of San Jose, Calif. Such a device provides sufficient I/O to communicate with each of one or more image sensors  901   f   1 ,  901   f   2  independently and thus allow simultaneous operation of each imager. Communication with each imager may be serial (optionally LVDS) or parallel. The FPGA may be programmed to implement a microprocessor to execute image analysis software. 
     Significant performance improvement in image analysis algorithm execution can be gained by using an FPGA over a conventional DSP or microcontroller. Increases in computational capability and efficiency may allow the use of higher resolution arrays or the implementation of more sophisticated algorithms which may increase the performance of the system. Higher performance may allow simultaneous analysis of images with acquisition eliminating the need to store full images to memory and thus potentially reducing memory cost. Finally, higher performance and efficiency may also allow the provision of more functionality or additional efficiency. 
     For a first example of the performance improvements realized with an FPGA consider a filter used in a moisture sensing application to detect edges which is implemented as a 3×3 kernel as described in U.S. Pat. No. 6,923,027, entitled Moisture Sensor and Windshield Fog Detector Using an Image Sensor, commonly assigned and herby incorporated by reference. Traditional software implementation of this filter requires sequential multiplication of a coefficient to neighboring pixels and accumulation of the products. This process must be preformed for every pixel in the image thus resulting in a very computationally intensive algorithm. With an FPGA, this filter may be implemented in digital logic, thus allowing parallel execution of the kernel computation and reducing overall processing time. 
     In a known exterior light control system, as described in commonly assigned U.S. patent application Ser. No. 10/645,801, the disclosure of which is incorporated in its entirety herein by reference, detection of oncoming headlights and preceding taillights is accomplished by looking for brightness peaks in the image. Brightness peaks are detected by comparing the grey scale value of the current pixels with its neighboring pixels to determine if the current pixel is a peak. With a conventional microcontroller, these comparisons are typically made sequentially. Since the test is performed on every non-zero pixel, the process can be computationally time consuming. With an FPGA, the peak-detect comparisons may be much more efficient by implementing parallel comparisons between the current pixel and its neighbors in circuitry, thereby increasing the performance of the device. 
     As a final example of the use of a FPGA consider the probability function based algorithms and neural network analysis techniques described in the previously referenced &#39;879 patent application. Neural network implementation requires the computation of several dot-products between an input vector and a weight vector. Each of these dot products must be computed by sequential multiply-accumulate operations on a conventional microcontroller or DSP. However, with an FPGA the computation of these dot products may be performed in parallel or at least partially in parallel by implementing several multipliers which operate simultaneously. In smaller FPGAs sufficient resources may not be available to implement all the desired hard wired functions. However, these devices can be partially reprogrammed on-the-fly when different functions are required. For example, the device can be programmed to implement a kernel filter for moisture sensing and later reprogrammed implement a peak-detect when headlamp control analysis is being performed. 
       FIG. 9   g  illustrates another embodiment of a mother board/imager board interconnection supporting one or more image sensors  901   g   1 ,  901   g   2  with a processor  930   g  local to the image sensors. In this case, the image sensors are connected by a common bus, similar to the embodiments of  FIG. 9   d , however, each image sensor is connected to the second processor  930   f  directly. As with the other embodiments discussed herein, multiple image sensors may share a power supply  924   g , an oscillator  920   g , a main processor  902   g  and second processor  930   g . 
     Several commercially available image sensors utilize a parallel bus for communication of image data. These devices typically use a 4, 8, or 10 bit wide bus. An example image sensor utilizing a parallel bus is a CIF format image sensor part number MI-0111 available from Micron, Inc. of Boise, Id. As shown in  FIG. 9   h , one or more parallel bus image sensors  901   h   1 ,  901   h   2  can be used more effectively when a second processor  930   h  is located on a common circuit board with the image sensors. As with the other embodiments discussed, multiple image sensors may share a common bus  950   h , power supply  924   h , oscillator  920   h , a main processor  902   h  and a second processor  930   h . Multiple image sensors with a parallel bus may also be connected individually to second processor  930   h  as is the case with the serial bus image sensors shown in  FIG. 9   f . In situations where parallel bus image sensors are used and a second processor  930   h  cannot be mounted on a common circuit board, a flex circuit cable may be used to connect the systems or a parallel-to-serial converter IC, such as the National Semiconductor DS92LV1021 may be used to convert the parallel data bus to an LVDS bit stream. 
     One disadvantage of the use of an LVDS serial bus as shown in  FIGS. 9   b ,  9   c  and  9   e  over the single ended bus of  FIG. 9   a  is the increase in the number of wires required to transmit the signals. The additional wires may increase the cost of the related wiring harness and may make wire routing more difficult. This limitation can be overcome by encoding the clock signal SPSCLK onto the same line as the data signal MOSI through Manchester coding or other similar means. In this case the transmitted bit rate is doubled in exchange for combining the clock or data into a single signal. In most cases the doubled rate data can still be robustly transmitted through an LVDS link. This embodiment is illustrated in  FIG. 9   i . The MOSI  904   i  and SPSCLK  905   i  signals are combined onto a single signal  942   i  using a Manchester encoder/decoder  940   i . An example Manchester encoder/decoder is part number HD-15530 available from Intersol. Signal  942   i  is converted to LVDS by transceiver  908   i  and transmitted to the imager subassembly. LVDS transceiver  906   i  restores single ended signal  942   i  and Manchester encoder/decoder  941   i  restores signals MOSI  904   i  and SPSCLK  905   i . It is envisioned that LVDS transceivers  941   i  or  940   i  may be combined with Manchester encoders  906   i  or  908   i  and either or both of these may be combined with the image sensor  901   i  or the processor  902   i . This scheme may also be applied with any of the previously disclosed embodiments including one or more image sensors and processors. 
     With reference to  FIG. 10 , another embodiment of an automatic vehicle equipment control system  1000  is depicted comprising a mother board  1005  interconnected with an imager board  1035  via a mother board/imager board interconnection  1045 . A breakaway board  1012  is depicted prior to breaking away from the mother board. The mother board further comprises a vehicle bus interface  1010 , vehicle equipment connectors  1007 , a processor  1008 , a enhanced transceiver  1009 , an ambient light sensor  1011  and an electro-optic element drive circuit  1014 . The breakaway board comprises a glare light sensor. When broken away, the breakaway board may be interconnected to the mother board as shown with regard to  FIGS. 5   a  and  5   b  with reference to the glare sensor board  512   a . 
     Turning now to  FIGS. 11   a  and  11   b , another embodiment of a mother board  1105   a ,  1105   b  is depicted to comprise all components mounted on a first side  1105   a   1 . Even the glare light sensor  1136   a ,  1136   b  is mounted to the first side and is aligned with a hole through the mother board such that light rays are detectable in a desired direction generally rearward of a controlled vehicle. As can be seen, there are no components mounted to the second side  1105   b   2 . This configuration is preferable in regard to manufacturing of certain embodiments. The mother board further comprises an imager board interconnection connector  1106   a , vehicle equipment connectors  1107   a , a processor  1108   a , a enhanced transceiver  1109   a , a surface mount ambient light sensor  1111   a , a reverse surface mount glare light sensor  1113   a  and an electro-optic mirror element drive circuit  1114   a.    
     Although the present invention has been described with reference to various embodiments and specific examples, it should be understood that the scope of the present invention should not be limited to the specific teachings herein. Equivalents may occur to one skilled in the art upon reading this detail description in light of the drawings and appended claims. The scope of the invention is intended to be construed in light of the doctrine of equivalents as define in evolving case law.