It Takes Two to Tango

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Maximillian Townsend
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1 It Takes Two to Tango Dual Linescan Architecture Vision 006 Stuttgart November 7, 006 Agenda Introduction Historical Trends in Machine Vision Problem: Too much noise and too few photons Overview of Dual Linescan Architecture Pros/cons of Dual Linescan Architecture Images comparing performance between Dual Linescan and Standard Linescan Architectures Question and Answer Period 1

2 Linescan Cameras More than most other types of applications, linescan applications are starved for photons Line rates are typically 100X to 1000X greater than frame rates Illumination is expensive and potentially a safety hazard Image quality is as important as other applications Le ns Object/Web Scan area Historical Trends in Linescan More responsivity Less signal electrons Higher photon shot noise relative to camera output

3 Historical Trends in Linescan More responsivity Less signal electrons Higher read noise relative to camera output Problem: Too much noise, too few photons If these preceding trends continue the camera s read noise and photon shot noise will exceed the digital detection threshold of machine vision applications This is already being evidenced with companies switching from linescan technology to TDI technology 3

4 Solution: Dual Linescan Architecture Breaks the shot noise vs. responsivity barrier Breaks the read noise vs. responsivity barrier Random Noise Floor and CCE of Successive Camera Generations Random Noise Floor (digital counts pk-pk) uv/e.5 uv/e 5 uv/e 10 uv/e 13.5 uv/e Spyder3 GigE (dual linescan) 13.5 uv/e Responsivity (a.u.) Dual Linescan Architecture This patented architecture contains two arrays of pixels 4

5 Dual Linescan Architecture Each array is connected to a selectable delay that either allows charge through or delays the changes by one scan line Dual Linescan Architecture Signal from the two arrays one delayed and one not are combined into a single output. Effectively doubling your responsivity. 5

6 Dual Linescan Example time=0 time=1 S Direction of web travel Delay time=0 time=1 Benefits of Dual Linescan X the responsivity X improvement in dynamic range in light starved applications v improvement in shot noise Better blue and UV response vs. TDI devices Maintained exposure control capability vs. TDI Selectable delay line maintains bi-directionality 6

Shortcomings of Dual Linescan Dark current is double This is mitigated because most applications benefit from maximizing speed. Faster speeds lead to lower dark current levels.

7 Shortcomings of Dual Linescan Dark current is double This is mitigated because most applications benefit from maximizing speed. Faster speeds lead to lower dark current levels. Maximized at two outputs per sensor This can be overcome by summing digitally off-chip; however, the on-chip merge improves SNR by a factor of versus, while off-chip merge improves SNR by a factor of v Dual Linescan in Action Dual Linescan Single Linescan Actual images from Spyder3 GigE camera Images shown illustrate X greater responsivity All camera parameters and test conditions are the same 7

Dark Current is X greater in dual linescan.

8 Dual Linescan in Action Dual Linescan Single Linescan Average_D (1-bit): Dark_Noise_D (rms): Forced offset_d: 80.09DN 14.7DN 70.00DN Average_S (1-bit): Dark_Noise_S (rms): Forced offset_s: 74.63DN 14.14DN 70.00DN Noise is comparable. Dark Current is X greater in dual linescan. Dual Linescan in Action Dual Linescan Single Linescan Average_D (1-bit): Total_Noise_D (rms): 3854DN 36.34DN Average_S (1-bit): Total_Noise_S (rms): 1959DN 7.7DN Responsivity has doubled as expected. 8

Dual Linescan Shot Noise Calculation Total _ Noise = Dark _ Noise + Shot _ Noise = Total _ Noise Single Linescan Shot _ Noise Dark _ Noise ( 36.34) ( 14. 7) Shot _ Noise _ D = Shot _ Noise _ D = 33.

9 Dual Linescan Shot Noise Calculation Total _ Noise = Dark _ Noise + Shot _ Noise = Total _ Noise Single Linescan Shot _ Noise Dark _ Noise ( 36.34) ( 14. 7) Shot _ Noise _ D = Shot _ Noise _ D = 33. DNrms ( 7.7) ( ) Shot _ Noise _ S = Shot _ Noise _ S = 3. 31DNrms Shot _ Noise _ D Shot _ Noise = Shot _ Noise _ S 33. Shot _ Noise = 3.31 Shot _ Noise =1.449 Responsivity doubled, but shot noise only increased by~v= Therefore, signal to shot noise ratio improved by ~. Thank you for you time! Come see our Spyder3 GigE camera demonstration at Stand # Featuring dual linescan technology. Any Questions? 9

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