KAC-06040_16 Datasheet, PDF (17/43 Pages) ON Semiconductor – CMOS Image Sensor

KAC−06040
The different signal levels are determined by varying the
integration time. The sensor saturation level is (1023-dark
offset). The dark offset is subtracted from the image for the
following M_AVG and L_AVG.
• The integration time is varied until the integration time
required to reach the 70% saturation is determined.
M_AVG = the active array mean at the 70% saturation
integration time.
• The integration is set to 1/14 (5% exposure point).
L_AVG = meant at the 5% exposure point.
• PRNL (@ 5% saturation) = ((L_AVG/M_AVG) ⋅ (14/1) −1)
⋅ 100
12) Maximum Gain Difference between Outputs
The LVDS outputs contain no gain or offset error since
these are purely digital segmentations. The predominant
output mismatch comes from the pixel array readout
segmentation. The sensor contains two ADC banks and four
channels of analog line stores in its highest frame rate
configuration, Tri−Scan. The sensor is factory calibrated to
match the gain differences between all four possible gain
channels. The gain variations are manifest as an every 4^th
row gain pattern. In tri−scan, and an even/odd row gain
difference in Dual−Scan. The sensor is factory calibrated to
match the four possible row gains. This test is performed in
Tri−Scan mode to test the worst case gain error including all
possible 4 row gains after the calibration has been applied.
The sensor is illuminated at 70% of saturation. The entire
test frame ROI into 4 groups of every 4^th row. The first row
group(average) is used as a reference and the following three
row groups are compared to the first. The largest error is
reported.
ǒ Ǔ Second Row Average
First Row Average ^{* 1 @ 100}
ǒ Ǔ Third Row Average
First Row Average ^{* 1 @ 100}
ǒ Ǔ Fourth Row Average
First Row Average ^{* 1 @ 100}
13) Photodiode Dark Current
The photodiode dark current is measured in rolling shutter
read out mode using 105 ms integration time and an analog
gain = 8. The value is converted to electrons/pix/sec using
the formula:
el−per−DN (gain=8)
Photodiode Dark Current + Aver. Signal (DN) @ _{0.105 seconds}
where ‘average signal (DN)’ is the average of all pixels in
the sensor array, and ‘el-per-DN (gain=8)’ is measured on
each sensor using the photon transfer method.
14) Storage Node Dark Current
The storage node dark current is measured in global
shutter read out mode using a special timing mode to prevent
the photodiode dark current from being transferred to the
storage node. In global shutter mode, the integration time of
the storage node is the time it takes to read out a frame. The
sensor analog gain is set to 2:
el−per−DN (gain=2)
Storage Node Dark Current + Aver. Signal (DN) @ _{0.138 seconds}
where ‘average signal (DN)’ is the average of all pixels in
the sensor array and ‘el-per-DN (gain=2)’ is measured on
each sensor using the photon transfer method.
15) Lag
Lag is measured as the number of electrons left in the
photodiode after readout when the sensor is illuminated at
70% of Photodiode Charge Capacity.
Analog gain is set to 8. With no illumination a 64 average
dark image is recorded (Dark_ref). The ‘el-per-DN’ is
measured using the photon transfer method.
Illumination is adjusted blink every other frame such that
the mean image output is 70% of the Photodiode Charge
Capacity for even frames, and with no illumination for odd
frames. A 64 frame average of Odd Dark Frames is recorded
as Dark_Lag.
Lag + (Dark_Lag * Dark_Ref) @ el−per−DN
Units : Electrons rms
16) Photodiode Charge Capacity
The sensor analog gain is reduced to < 1 to prevent ADC
clipping at 1023 dn. The ‘el-per-DN’ is measured using the
photon transfer method. The sensor is illuminated at a light
level ∼1.5x the illumination at which the pixel output no
longer linearly changes with illumination level.
The Photodiode Charge Capacity is equal to the average
signal (DN) ⋅ el-per-DN. Units: electrons rms.
17) Dark Field Faint Column/Row Defect
A 4 frame average, no illumination image is acquired at
one line time of integration. Major defective pixels are
removed (> 5 Sigma). All columns or rows are averaged
together. The average of the local ROI of 128 columns or
rows about the column/row being tested is determined. Any
columns/rows greater than the local average by more than
the threshold are identified.
18) Bright Field Faint Column/Row Defect
A 4 frame average, 70% illumination image is acquired at
one line time of integration. Major defective pixels are
removed (> 5 Sigma). All columns or rows are averaged
together. The average of the local ROI of 128 columns or
rows about the column/row being tested is determined. Any
columns/rows greater than the local average by more than
the threshold are identified.
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