A picture can say more than 1000 words comparing camera images. Jürgen Bretschneider, 2015

Transcription

1 A picture can say more than 1000 words comparing camera images Jürgen Bretschneider, 2015

2 Allied Vision Profile Foundation: 1989, Headquarters: Stadtroda (Germany) Employees: > 300 (2015) Know how: Development and production of high-quality digital cameras for industrial and scientific imaging Research & Development Hardware- and software development of digital cameras for the visible and the infrared spectrum Standard cameras and also camera solutions for OEM customers Production Service Company-owned production sites (cleanroom) in Stadtroda and Osnabrück (Germany), Burnaby BC (Canada) Consulting teams for distribution and support, worldwide, 24/5 Quality standards Compliance with ISO-9001 and ISO 13485

3 Measurement setup (Ulbricht sphere) EMVA 1288 standard unified method of measuring a camera s imaging performance Ulbricht sphere for C-/ CS- and F-Mount-cameras with homogeneous light source at 632 nm, 529 nm, 448 nm and 850 nm (NIR) Camera as black box (only pixel size and exposure time must be known) All measurements use cameras without protection or filter glass Calibration of the light source and setup of light intensity initially > 50 measured points to generate curves for sensitivity, linearity, temporal and spatial noise EMVA 1288 camera data sheet provides measured and derived EMVA data based on 5 cameras of the same type R, G, B, NIR

4 Simplified EMVA 1288 related camera model Noise Photon Shot Noise Temporal: dark noise, quantization noise Spatial: Dark Signal Non-Uniformity (DSNU) Photo Response Non-Uniformity (PRNU) Signal Digital value photons

5 Description of characteristic EMVA 1288 values Sensitivity threshold: point where signal equals temporal dark noise Saturation capacity: number of electrons that each pixel of an sensor holds, before reaching non-linear response Dynamic range (DYN): Ratio of the maximum signal (saturation capacity) to the minimum signal (temporal dark noise) Maximum signal-to-noise ratio (SNR): Ratio of the maximum signal (saturation capacity) to all noise sources Noise: Unwanted statistical variations of signal produced by the image sensor (temporal dark noise, photon shot noise and spatial noise, like DSNU and PRNU) Saturation Capacity DYN Dark Noise SNR max Saturation Capacity Dark Noise Photon Shot Noise

6 Description of characteristic EMVA 1288 values Saturation capacity Slope = Quantum Efficiency Gain SNR at saturation Noise Caused by irradiance: - Photon shot noise (temporal) - PRNU (spatial) SNR bit 60 db db 8 24 db 4 Dark noise Dark noise + Photon Shot noise Maximum signal Sensitivity threshold (SNR=1) Irradiance independent: - Dark noise (temporal) Sensitivity threshold Saturation point - DSNU (spatial)

7 EMVA 1288 DATA Prosilica GT2750

8 Photon transfer method: Noise as a measuring tool (example Manta G-223C) measured data: System Gain, QE, Temporal Dark Noise, Saturation Capacity, derived data: Sensitivity Threshold, DNR, SNR max System gain 1/K: [e-/dn] Quantum efficiency: [%] Sat. Capacity: [e-] [p~] dark noise: [DN] [e-] SNR max: [db] 6.646[bits] Sensitivity threshold: [e-] [p~] Dynamic Range DR: [db] [bits] Temporal dark noise System Gain QE Saturation Capacity

9 Spatial nonuniformity DSNU and PRNU (MG-223C) Spectrogram Method: analyse spatial nonuniformity DSNU and PRNU (vertically and horizontally) logarithmic histograms of spatial variations find outlier (Defect Pixels) Deviation Outliers Model Model DSNU = [DN] [e-] PRNU = [%]

10 Sensitivity curves of selected sensors Manta G-235C (CMOS IMX174LQJ) 448 nm 529 nm 632 nm QE = f (λ) Manta G-235B (CMOS IMX174LLJ) 529 nm 850 nm (NIR) Sensitivity estimation: S~QE/dark noise

11 EMVA data of selected Allied Vision cameras lowest threshold? 1 Sensitivity threshold [e-] Quantum Efficiency 529 nm] appears brightest? 1 Saturation Capacity [e- *1000] 1 SNR max [db] DNR max [db] Pixel area [µm²] Manta G-235C Manta G-223C Mako G-503C Mako G-192C Global Shutter Mako G-192C Rolling Shutter Manta G-201C Manta G-145C

12 Low-light performance of selected Allied Vision cameras Camera Manta G-235C IMX 174 Manta G-223C CMV 2000 Mako G-503C MT9P006 Mako G-192C GS EV76C570 Mako G- 192C RS EV76C570 Manta G-201C ICX274 Manta G-145C ICX285 Pixel area 34,34 µm² 30,25 µm² 4,84 µm² 20,25 µm² 20,25 µm² 19,36 µm² 41,60 µm² 1 MG-503C really so sensitive? camera Manta G-235C Manta G-223C Mako G-503C Mako G-192C Global Shutter Mako G-192C Rolling Shutter Manta G-201C Manta G-145C Sensitivity threshold 7,07 e [ p~] [e-] [p~] [e-] [p~] 22,8 [e-] 62 [p~] 9 [e-] 28 [p~] 9,5[e-] 30 [p~] 22,5 [e-] 56,92[p~] Title Presentation dd/mm/yyyy 12

13 Comparing images at low-light condition Mako G-192C GS Mako G-192C RS Manta G-235C Manta G-223C Test setup: Neon tube 5000K Kowa LM12SC 12mm 1" F1,8 24dB, 300us, Gamma 0,45 Manta G-145C Manta G-201C Mako G-503C

14 Comparing images at low-light condition 7 Mako G-192C GS 2 4 Mako G-192C RS 6 1 Manta G-235C 5 3 Manta G-223C Test setup: Neon tube 5000K Kowa LM12SC 12mm 1" F1,8 24dB, 300us, Gamma 0,45 Manta G-145C Manta G-201C Mako G-503C

15 Low-light performance adapted to photons/µm² camera Manta G-235C Manta G-223C Mako G-503C Mako G-192C Global Shutter Mako G-192C Rolling Shutter Manta G-201C Manta G-145C light densitiy Sensitivity threshold 0,33 p/µm² 1,35 p/µm² 2,51 p/ µm² 3,06 p/µm² 1,38 p/µm² 1,55 p/µm² 1,37 p/µm² Title Presentation dd/mm/yyyy 15 Sensitivity threshold (SNR = 1) will be reached earlier at less photons

16 Low-light performance adapted to photons/µm² QE camera Manta G-235C Manta G-223C Mako G-503C Mako G-192C Global Shutter Mako G-192C Rolling Shutter Manta G-201C Manta G-145C light densitiy Sensitivity threshold 0,33 p/µm² 1,35 p/µm² 2,51 p/ µm² 3,06 p/µm² 1,38 p/µm² 1,55 p/µm² 1,37 p/µm² Title Presentation dd/mm/yyyy 16 Sensitivity threshold (SNR = 1) will be reached earlier at less photons

17 Bright-light condition 1. high-speed application (shortest shutter time) and 2. high variation in light (high SNR) MG-503C really appears brightest? camera Saturation capacity nm) Manta G-235C [e-] [p~] Manta G-223C [e-] [p~] Mako G-503C 4677,3 [e-] 9300 [p~] Mako G-192C Global Shutter Mako G-192C Rolling Shutter Manta G-201C Manta G-145C 5900 [e-] [p~] [e-] [p~] 7200 [e-] [p~] [e-] [p~]

18 Comparing images at bright-light condition Application task: need for bright image at shortest possible shutter time, SNR isn t an issue Mako G-192C GS Mako G-192C RS Manta G-235C Manta G-223C Test setup: Neon tube 5000K Kowa LM12SC 12mm 1" F1,8 4ms Gamma 1,0 Manta G-145C Manta G-201C Mako G-503C

19 Comparing images at bright-light condition Mako G-192C GS Mako G-192C RS Manta G-235C 87 7 Manta G-223C Test setup: Neon tube 5000K Kowa LM12SC 12mm 1" F1,8 4ms Gamma 1,0 Manta G-145C Manta G-201C Mako G-503C

20 Bright-light performance adapted to photons/µm² camera Manta G- 235C Manta G- 223C light densitiy Saturation capacity 1572 p/ µm² 674 p/ µm² Mako G-503C 1921 p/ µm² Mako G-192C GS Mako G-192C RS Manta G- 201C Manta G- 145C 809 p/ µm² 1315p/µm² 1015 p/µm² 1105 p/µm²

21 Comparing images at bright-light condition Application task: high variation in lighting condition, high dynamic scenes, high SNR is needed Manta G-235C Mako G-503C ms/ 0 db gain/ Gamma 0.45 Test setup: Neon tube 5000K Kowa LM12SC 12mm 1" F1,8 images adjusted to 250 DN 12.5 ms/ 0 db gain/ Gamma 0.45

22 What about Dynamic at low illuminated image parts? Manta G-235C SNR max 45 db (7.5 bits) Mako G-192C RS SNR max 40 db (6.6 bits) Mako G-192C GS SNR max 38 db (6.3bits) Signal-to-Noise Ratio (SNR) Noise! Title Presentation dd/mm/yyyy 22

23 CCD artifacts blooming and smear Blooming: Charge overflow (> full well capacity) between neighboring pixels Corrective action: reduction of the incoming light Smear: During readout photons generate a charge in the vertical shift register Corrective action : increase of the exposure time, use of a mechanical or LCD shutter, use of flash illumination

24 blooming and smear test images of CCD and CMOS sensors Manta G-145C (ICX 285) Manta G-201C (ICX 274) Manta G-223C (CMV2000) Mako G-192C (EV76C570) Mako G-503C (MT9P006) Manta G-235C (IMX 174)

25 Global Shutter efficiency unwanted sensitivity Shutter efficiency = (1 - parasitic light sensitivity) Define how much the stored pixel value is distorted by incoming light during readout phase of the sensor when the shutter is closed Former CMOS global shutter sensors are affected by higher parasitic light sensitivity reduces the ability to use very short integration times to freeze motion E.g. datasheet of the CMOS sensor IBIS5-A-1300 specifies a parasitic sensitivity < 1% up to 400µs at 40 ms readout time In case of long exposure times, like 20 ms, parasitic sensitivity 400 µs is negligible, but in case of 2µs shutter time this leads to a strong vertical increase in brightness Nowadays CMOS global shutter sensors provide ratio of 1:2000 or better shutter efficiency IBIS5-A-1300:

26 Global Shutter efficiency of selected sensors Mako G-223B (CMV 2000) shutter time: 1µs Marlin F-131B (IBIS5-A-1300) shutter time: 2µs Mako G-030C (CMV300) shutter time: 83 µs Manta G-145B (ICX 285AL) shutter time: 20 µs parasitic sensitivity up to 400 µs! (readout time: 40 ms)

27 Meaning of measured values: Background and pitfalls Quantum Efficiency QE = f (λ) - Measured for monochrome cameras only at 529 nm and for color cameras at 632 nm, 529 nm, 448 nm - Please use sensitivity curve to estimate how the camera performs at other wavelengths Signal response vs. sensitivity: - Grey value generated at a certain exposure time has nothing to do with sensitivity - For purposes of comparison you have to consider Photon Shot Noise and Dark Noise Saturation capacity vs. sensitivity: - The lower the achievable saturation capacity, the earlier the maximum output level is reached - This does not mean, that a low saturation capacity implies a high sensitivity - Comparing Sensitivity threshold and saturation capacity of different cameras you have to consider Pixel area for the incoming light - light density photons/µm² Gain: - Higher gain does not mean increased sensitivity, since signal and noise are increased in the same ratio - Applying gain reduces the achievable saturation capacity of a camera - In case of sufficient image quality it is used to shorten the shutter time to prevent motion blur Tolerances: - Due to manufacturing tolerance of the sensor and camera electronics a real camera may differs from the EMVA1288 test results. The uncertainty in measurement of the QE values is up to 10%

28 EMVA1288 results and real application demands You always have to reconsider the optical set-up (lens, filters) and suitable Lighting - Consider Quantum Efficiency is a function of the wavelength Low-light applications: - Camera qualified with low Sensitivity threshold and high QE - Compare light densitiy Sensitivity threshold - Sensors with low temporal dark noise allows more gain without loosing to much image quality at shorter shutter time Bright-light applications: a) High-speed application - Need for a bright image at shortest possible shutter time, (SNR isn t an issue, 4-6 bit sufficent) camera is qualified with Low value of light densitiy Saturation capacity - Higher QE means less illumination or shorter shutter speed b) High variation in lighting condition: - High SNR and large saturation capacity are needed for dynamic scenes with different lighting situations

29 Thank You/Q&A Allied Vision Technologies GmbH Taschenweg 2a Stadtroda Germany