BASLER A601f / A602f

Transcription

1 Camera Specification BASLER A61f / A6f Measurement protocol using the EMVA Standard 188 3rd November 6 All values are typical and are subject to change without prior notice.

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3 CONTENTS Contents 1 Overview 1 Introduction 3 Basic Information Illumination Illumination Setup Basler-CameraTestTool Measurement of the Irradiance Characterizing Temporal Noise and Sensitivity Basic Parameters Total quantum efficiency Temporal dark noise Dark current Doubling temperature Inverse of overall system gain Inverse photon transfer Saturation capacity Spectrogram Non-Whiteness Coefficient Derived Data Absolute sensitivity threshold Signal to noise ratio Dynamic range Raw Measurement Data Mean gray value Variance of temporal distribution of gray values Mean of the gray values dark signal Variance of the gray values temporal distribution in dark Light induced variance of temporal distribution of gray values Light induced mean gray value Dark current versus housing temperature Characterizing Total and Spatial Noise Basic Parameters Spatial offset noise Spatial gain noise Spectrogram Spatial Noise Spatial Non-Whiteness Coefficient Raw Measurement Data Standard deviation of the spatial dark noise BASLER A61f / A6f I

4 CONTENTS 5.. Light induced standard deviation of the spatial noise Bibliography 35 II BASLER A61f / A6f

5 1 Overview 1 Overview Basler A61f / A6f Item Symbol Typ. 1 Std. dev. Unit Remarks Temporal Noise Parameters Total quantum efficiency (QE) η 3 TBD % λ = 545 nm Inverse of overall system gain 1 K e DN Temporal dark noise σ d e Saturation capacity µ e.sat e Spatial Noise Parameters Spatial offset noise, DSNU 188 σ o e Spatial gain noise, PRNU 188 S g 1.1. % Derived Parameters Absolute sensitivity threshold µ p.min 37 TBD p λ = 545 nm Dynamic range DYN out.bit 8.8. bit Table 1: Most important specification data Operating Point Item Symbol Remarks Video output format 1 bits/pixel(mono16) Gain Offset 768 Exposure time T exp 1. µs to 53.5 ms Table : Used camera operating point 1 The unit e is used in this document as statistical measured quantity. The standard deviation was calculated from a sampling of 1 cameras. BASLER A61f / A6f 1-1

6 Introduction Introduction This measurement protocol describes the specification of the Basler A61f / A6f cameras. The measurement methods are conform to the EMVA Standard 188, the Standard for Characterization and Presentation of Specification Data for Image Sensors and Cameras (Release A1.3) of the European Machine Vision Association (EMVA) [1]. The most important specification data of the Basler A61f / A6f cameras are summarised in the table 1. - BASLER A61f / A6f

7 3 Basic Information 3 Basic Information Basic Information Vendor Basler Model A61f / A6f Type of data presented Typical Number of samples 1 Sensor Micron MT9V43 Sensor type CMOS Sensor diagonal Diagonal 8 mm (Type 1/) Indication of lens category to be used C-Mount Resolution 656 x 491 pixel Pixel width 9. µm Pixel height 9. µm Readout type - Transfer type - Shutter type Global Shutter Overlap capabilities Maximum frame rate 6 frames/second General conventions Interface type Firewire 1394a Table 3: Basic Information BASLER A61f / A6f 3-3

8 3.1 Illumination 3.1 Illumination Illumination Setup Basler-CameraTestTool The illumination during the test of one camera was fixed. The drift of the illumination over a long time and after exchange of the lamp is measured by a reference Basler A6fc camera. The reference camera provides an intensity factor which was used to calculate the irradiance for each camera measurement. Light source Wavelength λ 545 nm Wavelength variation λ 5 nm f-number f # 8 = 8 mm/35 mm Table 4: Light source 3.1. Measurement of the Irradiance The irradiance was measured using a Radiometer IL17 from International Light Inc. (Detector: SEL33 #685; Input optic: W #9461; Filter: F #1487; regular calibration). The accuracy of the Radiometer is specified as ±3.5%. In figure 1 the measured irradiance is plotted. 45x1-3 A6xf (1 cameras), Irradiance Irradiance [W/m^] Measurement Figure 1: Irradiance for each camera measurement. The the error of all calculated values using the amount of light falling on the sensor are dependent of the accuracy of the irradiance measurement. 4-4 BASLER A61f / A6f

9 4 Characterizing Temporal Noise and Sensitivity 4 Characterizing Temporal Noise and Sensitivity 4.1 Basic Parameters Total quantum efficiency Total quantum efficiency for one fixed wavelenght Total quantum efficiency η(λ) in [%] for monochrome light at λ = 545 nm. With a wavelength variation of λ = 5 nm. A6xf (1 cameras), Quantum efficiency 35 Quantum efficiency [%] Camera A6xf (1 cameras), Quantum efficiency histogram 15 Number Quantum efficiency [%] Figure : Total quantum efficiency (QE) Item Symbol Typ. Std. dev. Unit Remarks Total quantum efficiency (QE) η 3 TBD % λ = 545 nm Table 5: Total quantum efficiency (QE) The main error of the total quantum efficiency η is related to the error of the measurement of the illumination described in section 3.1. BASLER A61f / A6f 4-5

10 4.1 Basic Parameters Total quantum efficiency versus wavelength of the light Total quantum efficiency η(λ) in [%] for monochrome light versus wavelength of the light in [nm]. 35 A6xf (1 cameras), Quantum efficiency Quantum efficiency [%] Wavelength [nm] Figure 3: Irradiance for each camera measurement. The curve of the total quantum efficiency versus the wavelength in figure 3 was calculated from the one measured total quantum efficiency as presented in section For the shape of the curve the data from the sensor data sheet was used. 4-6 BASLER A61f / A6f

11 4.1 Basic Parameters 4.1. Temporal dark noise Standard deviation of the temporal dark noise σ d time zero in [ e ]. referenced to electrons for exposure A6xf (1 cameras), Std. temporal dark noise Std. Temporal dark noise [e-] Camera A6xf (1 cameras), Std. temporal dark noise histogram 5 Number Std. Temporal dark noise [e-] Figure 4: Temporal dark noise Item Symbol Typ. Std. dev. Unit Remarks Temporal dark noise σ d e Table 6: Temporal dark noise BASLER A61f / A6f 4-7

12 4.1 Basic Parameters Dark current Dark current N d3 for a housing temperature of 3 C in [e /s]. Not measured! Doubling temperature Doubling temperature k d of the dark current in [ C]. Not measured! 4-8 BASLER A61f / A6f

13 4.1 Basic Parameters Inverse of overall system gain Inverse of overall system gain 1 K in [ e DN ]. Inverse conversion gain [e-/dn] A6xf (1 cameras), Inverse conversion gain Camera A6xf (1 cameras), Inverse conversion gain histogram Number Inverse conversion gain [e-/dn] Figure 5: Inverse of overall system gain Item Symbol Typ. Std. dev. Unit Remarks Inverse of overall system gain 1 K e DN Table 7: Inverse of overall system gain BASLER A61f / A6f 4-9

14 4.1 Basic Parameters Inverse photon transfer 1 Inverse photon transfer in [ ] p ηk DN. A6xf (1 cameras), Inverse photon transfer Inverse photon transfer [p~/dn] Camera A6xf (1 cameras), Inverse photon transfer histogram 15 Number Inverse photon transfer [e-/dn] Figure 6: Inverse photon transfer Item Symbol Typ. Std. dev. Unit Remarks Inverse photon transfer 1 ηk TBD Table 8: Inverse photon transfer p DN λ = 545 nm 1 The main error of the inverse photon transfer is related to the error of the measurement of the illumination described in section ηk BASLER A61f / A6f

15 4.1 Basic Parameters Saturation capacity Saturation capacity µ e.sat referenced to electrons in [ e ]. A6xf (1 cameras), Saturation capacity Saturation capacity [e-] 5x Camera A6xf (1 cameras), Saturation capacity histogram 5 Number x1 3 Saturation apacity [e-] Figure 7: Saturation capacity Item Symbol Typ. Std. dev. Unit Remarks Saturation capacity µ e.sat e Table 9: Saturation capacity BASLER A61f / A6f 4-11

16 4.1 Basic Parameters Spectrogram Spectrogram referenced to photons in [p ] is plotted versus spatial frequency in [1/pixel] for no light, 5% saturation and 9% saturation. A6xf (1 cameras), FFT dark 14 FFT amplitude [p~] All Mean A6xf (1 cameras), FFT dark FFT amplitude [p~] All Mean Figure 8: Spectrogram referenced to photons for no light 4-1 BASLER A61f / A6f

17 4.1 Basic Parameters A6xf (1 cameras), FFT saturation.5 FFT amplitude [p~] 15x All Mean A6xf (1 cameras), FFT saturation.5 FFT amplitude [p~] All Mean Figure 9: Spectrogram referenced to photons for 5% saturation BASLER A61f / A6f 4-13

18 4.1 Basic Parameters 3x1 3 A6xf (1 cameras), FFT saturation.9 FFT amplitude [p~] All Mean A6xf (1 cameras), FFT saturation.9 FFT amplitude [p~] All Mean Figure 1: Spectrogram referenced to photons for 9% saturation 4-14 BASLER A61f / A6f

19 4.1 Basic Parameters Non-Whiteness Coefficient The non-whiteness coefficient is plotted versus the number of photons µ p in [p ] collected in a pixel during exposure time. A6xf (1 cameras), Non whiteness 4 Non whiteness x1 3 Mean photon [Photons/pixel] Figure 11: Non-whiteness coefficient BASLER A61f / A6f 4-15

20 4. Derived Data 4. Derived Data 4..1 Absolute sensitivity threshold Absolute sensitivity threshold µ p.min (λ) in [ p ] for monochrome light versus wavelength of the light in [nm]. µ p.min = σ d (1) η Absolute sensitivity threshold [p~] A6xf (1 cameras), Absolute sensitivity threshold Camera A6xf (1 cameras), Absolute sensitivity threshold histogram 15 Number Absolute sensitivity threshold [p~] Figure 1: Absolute sensitivity threshold Item Symbol Typ. Std. dev. Unit Remarks Absolute sensitivity threshold µ p.min 37 TBD p λ = 545 nm Table 1: Absolute sensitivity threshold 4-16 BASLER A61f / A6f

21 4. Derived Data 4.. Signal to noise ratio Signal to noise ratio SNR y (µ p ) is plotted versus number of photons µ p collected in a pixel during exposure time in [p ] for monochrome light with the wavelength λ given in [ nm]. The wavelength should be near the maximum of the quantum efficiency. A : SNR y = µ y µ y.dark σ y () B : SNR y = ηµ p (ηµp + σ d ) (3) Figure 13 shows the signal to noise ratio SNR y for monochrome light with the wavelength λ = 545 nm. 8 A6xf (1 cameras), SNR SNR [bit] 6 4 A B Mean photon [bit] Figure 13: Signal to noise ratio BASLER A61f / A6f 4-17

22 4. Derived Data A6xf (1 cameras), SNR SNR Mean photon [Photons/pixel] A B Figure 14: Signal to noise ratio 4-18 BASLER A61f / A6f

23 4. Derived Data 4..3 Dynamic range Dynamic range DYN out.bit in [ bit]. DYN out = µ e.sat σ d (4) DYN out.bit = log (DYN out ) (5) A6xf (1 cameras), Dynamic range output Dynamic range output [bit] Camera 3 A6xf (1 cameras), Dynamic range output histogram 5 Number Dynamic range output [bit] Figure 15: Output dynamic range Item Symbol Typ. Std. dev. Unit Remarks Output dynamic range DYN out.bit 8.8. bit Table 11: Output dynamic range BASLER A61f / A6f 4-19

24 4.3 Raw Measurement Data 4.3 Raw Measurement Data Mean gray value Mean gray value µ y (µ p ) in [DN] is plotted versus number of photons µ p in [p ] collected in a pixel during exposure time. A6xf (1 cameras), Mean gray value bright Mean gray value bright [DN] x1 3 Mean photon [Photons/pixel] Figure 16: Mean gray values of the cameras with illuminated pixels 4- BASLER A61f / A6f

25 4.3 Raw Measurement Data 4.3. Variance of temporal distribution of gray values Variance of temporal distribution of gray values σy.temp(µ p ) in [DN ] is plotted versus number of photons µ p in [p ] collected in a pixel during exposure time. A6xf (1 cameras), Variance gray value bright Variance gray value bright [DN^] x1 3 Mean photon [Photons/pixel] Figure 17: Variance values of temporal distribution of gray values with illuminated pixels Saturation Capacity The saturation point is defined as the maximum of the curve in the diagram 17. The abscissa of the maximum point is the number of photons µ p.sat where the camera saturates. The saturation capacity µ e.sat in electrons is computed according to the mathematical model as: µ e.sat = ηµ p.sat (6) BASLER A61f / A6f 4-1

26 4.3 Raw Measurement Data Mean of the gray values dark signal Mean of the gray values dark signal µ y.dark (T exp ) in [DN] is plotted versus exposure time in [s]. A6xf (1 cameras), Mean gray value dark Mean gray value dark [DN] x1 3 Exposure time [us] Figure 18: Mean gray values of the cameras in darkness 4- BASLER A61f / A6f

27 4.3 Raw Measurement Data Variance of the gray values temporal distribution in dark Variance of the gray values temporal distribution in dark σy.temp.dark(t exp ) in [DN ] plotted versus exposure time T exp in [s]. is A6xf (1 cameras), Variance gray value dark Variance gray value dark [DN^] x1 3 Exposure time [us] Figure 19: Variance values of temporal distribution of gray values in darkness Temporal Dark Noise The dark noise for exposure time zero is found as the offset of the linear correspondence in figure 19. Match a line (with offset) to the linear part of the data in the diagram. The dark noise for exposure time zero σd is found as the offset of the line divided by the square of the overall system gain K. σ d = σ y.temp.dark (T exp = ) K (7) BASLER A61f / A6f 4-3

28 4.3 Raw Measurement Data Light induced variance of temporal distribution of gray values The light induced variance of temporal distribution of gray values in [DN ] versus light induced mean gray value in [DN]. is plotted Variance gray value (bright - dark) [DN^] A6xf (1 cameras), Diff variance vs diff mean gray value Mean gray value (bright - dark) [DN] Figure : Light induced variance of temporal distribution of gray values versus light induced mean gray value The overall system gain K is computed according to the math- Overall System Gain ematical model as: K = σ y.temp σ y.temp.dark µ y µ y.dark (8) which describes the linear correspondence in the diagram. Match a line starting at the origin to the linear part of the data in this diagram. The slope of this line is the overall system gain K. 4-4 BASLER A61f / A6f

29 4.3 Raw Measurement Data Light induced mean gray value The light induced mean gray value µ y µ y.dark in [ DN] is plotted versus the number of photons collected in a pixel during exposure time Kµ p in [ p ]. A6xf (1 cameras), Difference mean gray value Mean gray value (bright - dark) [DN] x1 3 Mean photon [Photons/pixel] Figure 1: Light induced mean gray value versus the number of photons Total Quantum Efficiency the mathematical model as: The total quantum efficiency η is computed according to η = µ y µ y.dark Kµ p (9) which describes the linear correspondence in the diagram 1. Match a line starting at the origin to the linear part of the data in this diagram. The slope of this line divided by the overall system gain K yields the total quantum efficiency η. The number of photons µ p are calculated using the model for monochrome light. The number of photons Φ p collected in the geometric pixel per unit exposure time [p /s] is given by Φ p = EAλ (1) hc with the irradiance E on the sensor surface [W/m ], the area A of the (geometrical) pixel [m ], the wavelength λ of light [m], the Planck s constant h Js and the speed of light c m/s. The number of photons can be calculated by µ p = Φ p T exp (11) BASLER A61f / A6f 4-5

30 4.3 Raw Measurement Data during the exposure time T exp. Using equation 9 and the number of photons µ p, the total quantum efficiency η can be calculated as η = hc 1 AT exp E 1 λ µ p µ y.dark. (1) K Dark current versus housing temperature Logarithm to the base of the dark current in [e /s] versus deviation of the housing temperature from 3 C in [ C] Not measured! 4-6 BASLER A61f / A6f

31 5 Characterizing Total and Spatial Noise 5 Characterizing Total and Spatial Noise 5.1 Basic Parameters Spatial offset noise Standard deviation of the spatial offset noise σ o referenced to electrons in [ e ]. 5 A6xf (1 cameras), DSNU188 DSNU188 [e-] Camera A6xf (1 cameras), DSNU188 histogram Number DSNU188 [e-] Figure : Spatial offset noise ( DSNU 188 ) Item Symbol Typ. Std. dev. Unit Remarks Spatial offset noise ( DSNU 188 ) σ o e Table 1: Spatial offset noise ( DSNU 188 ) BASLER A61f / A6f 5-7

32 5.1 Basic Parameters 5.1. Spatial gain noise Standard deviation of the spatial gain noise S g in [ %]. A6xf (1 cameras), PRNU PRNU188 [%] Camera A6xf (1 cameras), PRNU188 histogram 15 Number PRNU188 [%] Figure 3: Spatial gain noise ( PRNU 188 ) Item Symbol Typ. Std. dev. Unit Remarks Spatial gain noise ( PRNU 188 ) S g 1.1. % Table 13: Spatial gain noise ( PRNU 188 ) 5-8 BASLER A61f / A6f

33 5.1 Basic Parameters Spectrogram Spatial Noise Spectrogram referenced to photons in [p ] is plotted versus spatial frequency in [1/pixel] for no light, 5% saturation and 9% saturation. A6xf (1 cameras), Spatial FFT dark 6 FFT amplitude [p~] All Mean A6xf (1 cameras), Spatial FFT dark FFT amplitude [p~] All Mean Figure 4: Spectrogram referenced to photons for no light BASLER A61f / A6f 5-9

34 5.1 Basic Parameters A6xf (1 cameras), Spatial FFT saturation.5 FFT amplitude [p~] 15x All Mean A6xf (1 cameras), Spatial FFT saturation.5 FFT amplitude [p~] All Mean Figure 5: Spectrogram referenced to photons for 5% saturation 5-3 BASLER A61f / A6f

35 5.1 Basic Parameters 3x1 3 A6xf (1 cameras), Spatial FFT saturation.9 FFT amplitude [p~] All Mean A6xf (1 cameras), Spatial FFT saturation.9 FFT amplitude [p~] All Mean Figure 6: Spectrogram referenced to photons for 9% saturation BASLER A61f / A6f 5-31

36 5.1 Basic Parameters Spatial Non-Whiteness Coefficient The non-whiteness coefficient is plotted versus the number of photons µ p in [p ] collected in a pixel during exposure time. 8 A6xf (1 cameras), Spatial non whiteness Spatial non whiteness x1 3 Mean photon [Photons/pixel] Figure 7: Spatial Non-whiteness coefficient 5-3 BASLER A61f / A6f

37 5. Raw Measurement Data 5. Raw Measurement Data 5..1 Standard deviation of the spatial dark noise Standard deviation of the spatial dark noise in [DN] versus exposure time in [s]. A6xf (1 cameras), Spatial std gray value dark Spatial std gray value dark [e-] x1 3 Exposure time [us] Figure 8: Standard deviation of the spatial dark noise From the mathematical model, it follows that the variance of the spatial offset noise σ o should be constant and not dependent on the exosure time. Check that the data in the figure 8 forms a flat line. Compute the mean of the values in the diagram. The mean divided by the conversion gain K gives the standard deviation of the spatial offset noise σ o. DSNU 188 = σ o = σ y.spat.dark K The square of the result equals the variance of the spatial offset noise σo. (13) BASLER A61f / A6f 5-33

38 5. Raw Measurement Data 5.. Light induced standard deviation of the spatial noise Light induced standard deviation of the spatial noise in [DN] versus light induced mean of gray values [DN]. Std. dev. gray value (bright - dark) [DN] A6xf (1 cameras), Spatial gain noise Mean gray value (bright - dark) [DN] Figure 9: Light induced standard deviation of the spatial noise The variance coefficient of the spatial gain noise Sg or its standard deviation value S g respective, is computed according to the mathematical model as PRNU 188 = S g = σ y.spat σ y.spat.dark µ y µ y.dark, (14) which describes the linear correspondence in the figure 9. Match a line through the origin to the linear part of the data. The line s slope equals the standard deviation value of the spatial gain noise S g BASLER A61f / A6f

39 REFERENCES References [1] EUROPEAN MACHINE VISION ASSOCIATION (EMVA): EMVA Standard Standard for Characterization and Presentation of Specification Data for Image Sensors and Cameras (Release A1.3). 6 BASLER A61f / A6f 5-35