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Lane Tracker Architecture, Next Generation

 
Lane Tracker System
Lane Tracker Optics
 
LASER Based Tracker
Color-Space Based Tracker
Color Filters' Transfer Functions
Area Array Timing & Geometry
TI's TC-286 Image Sensor
 Brief Specs
 
 
ThermoElectric Cooler Plot
 TI's TC-236 Image Sensor
used in the Quick Color Cam
socs043a.pdf  284kb
 

Next-Gen Lane Tracker will be Hybrid

The next generation Lane Tracker will be a duel mode hybrid, combining two different architectures: one for daylight and one for night time. 

The camera topology consists of a single color CCD area array, capable of randomly addressable scan lines; a day/nite filter selector; a relay lens system; and the taking lens (front glass). Attached in close proximity and alignment will be the special spread-beam LASER illuminator (for night time). 

The daylight approach uses the first three active scan lines of a NTSC tri-color CCD area array. The image data from the array's R, G, B, outputs will be processed for Color Space Translation such that only HUE is extracted and used for White/Yellow Lines detection. 

This approach has among its properties, the exclusion of vehicle shadowing from the White/Yellow Line boundary detection problem. That is to say, the confusion between longitudinal /near parallel vehicle shadowing and White/Yellow Line edge boundaries has long been a problem requiring lots of DSP processor time.

A second property is that it utilizes ambient light, reducing the complexity of the LASER only based approach.

The night time line detection system utilizes the LASER only based approach found in the previous generation Lane Tracker.

In this approach, unlike the aforementioned first gen lane Tracker, the linear CCD array is replaced with the color R,G, B, area array of the daytime system.

An examination of the spectral plot of the color CCD array reveals a high sensitivity to the LASER wavelength, 790nm, in the RGB filter's NIR "pop-up" region.

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Lane Tracker System (Next Gen)
TL Taking Lens (front lens) 
RL  Relay Lens
IFB  Image Fiber Bundle 
ALM  Alignment Mover
LOR  LASER Optical Rod 
CL  Collimating Lens
OF  Optical Filter (selectable)
CCD  Sensor 
TEC  Thermal Electric Cooler 
LD  LASER Diode 
ADC Analog to Digital Convertor
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Lane Tracker Front End 
Combination Camera
Click image to see larger version

 Combination Camera with Dual Filter Selector 

Filter F1 is a 3 stage Dielectric Optical Bandpass Filter Fc = 790 nm, HPWL = 10 nm; 

Filter F2 is an Infrared Cut Filter (Schott Colored Glass, IR Reject Filter).

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The Ideal Sensor
The ideal color area array sensor would have randomly addressable scan lines, such that the active image field could start at some arbitrary selected active scan line and either complete the field, or truncate the scan to from the very next line or any contiguous group of lines, i.e., the field could be from 1 line to 242 lines in length (typically, 3 lines). 

The practical reasoning behind this approach are several: 
1) random intermittent full image views of the roadway scene could be captured; 
2) this would allow greater control on light integration time, i.e., several line times to multiple field intervals n x 16.667msec.
 

Texas Instruments TC-286    Brief Specs
Hi-Res BCMD Image Sensor for NTSC Color Applications.
The less-than-ideal NTSC Sensor
Some standard NTSC RS-170A, CCD sensors can be used for this approach by, asynchronously restarting the frame transfer clock . The deficiency in this approach is the latency of the first 20 scan lines that make up the vertical interval. This would mean a fixed delay of 1,270 usec ( n x 63.5 usec) before active imaging takes place. 

Conclusions
In the practical world, this may not present a problem, that is, distance between measurements "D"--worst case--would be: assuming a total of [23 (20 + 3 scanlines) x 63.5 usec = 1,465 usec frame rate] @ 60 MPH = 88'/sec = 1,056 "/sec = 26,822 mm/sec, then D = 1.547" /sample or 39.30 mm/sample.

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HUE Extraction

1) Data Translation RGB - HSI Convertor DT7910 & ROM DT7971.

2) A real time SUM of Vectors circuit--analog or digital-- can also do the RGB - HSI conversion. 

Because this a radiometric not a photometric problem, the R G B inputs can have any weight, e.g.., equal weights R = 0.33, G = 0.33, B = 0.33.

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Roadway Shots
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Histogram of section of Yellow Line 
 
Histogram of section of White Line 
 
Histogram of section of Asphalt Pavement 
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LASER Based (Active) CCD Scanner
 


NIR LASER illuminates pavement on alternate scans; the resulting target image derives from the difference.
move your mouse over image for animation

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Passive CCD Scanner, Color Space Based  
 
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<--[See Test Video]--> 
Area Array Timing & Geometry
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Texas Instruments TC-286 
Hi-Res BCMD Image Sensor for NTSC Color Applications.
For Your Very Own DataSheet  (socs059.pdf ~125Kb)
  • 1/3 " image area; 680 (H) x 500 (V) Active Elements
  • 7.4 um Square Pixels
  • Random Line Addressable
  • 2000:1 Blooming Overload
  • Dynamic Range >70 dB
  • Dual Line Readout; 0 - 5 V Clocking Levels
  • First Samples ~ March 97; Delivery ~ August, 97; Cost~ $ 62.00
Subject: Addressable line-scan part from TI Date: Mon, 06 Jan 1997 From: Scott Johnson <sojo@ti.com> 

Glen,

After speaking with our CCD group, I found out that our TC286 has the addressable line scan incorporated into it. The datasheet is in our 1996 Area Array Sensor databook, or I have attached an electronic copy if you don't have the book. It looks like we will have preliminary samples in March, with projected production in the August timeframe. It looks like the part will sell for somewhere around $62. Please refer to one of our authorized distributors for an exact quote or give us a call if you have further questions. Our phone number is (972) 644-5580.

Regards, Scott Johnson Product Information Center 

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Color Filters, Transfer Functions showing NIR pop-up in the Passband
 
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Mascot

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Thermo Electric Cooler
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