Characterisation, Measurement & Analysis
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Sensor Signals Timing

Each sensor has different timing.
The real timing depends on:

  • Exposure Time (ET). This time is defined by xiAPI by (XI_PRM_EXPOSURE)
  • Data Readout Time (trd)
  • Transfer speed (MB/s) - depends on used interface
  • Amount of data transferred (MB) - depends on image resolution and number of bits transferred per pixel (BPP)

Free-Run mode (no trigger)

Each image exposition is started automatically when possible. This mode gives the highest fps (frames per second) that is possible on the sensor.

Exposure Overlapped with Data Readout Mode

This Overlapped mode gives the highest number of frames per second.

exposure_overlapped
Sensor timing in Exposure Overlapped with Data Readout Mode

In this mode the timing depends on minimum of Exposure Time and Data Readout Time.

Triggered mode without overlap

Each image exposition is triggered with input trigger signal.
This mode gives lower fps value compared to Free-Run mode.

Exposure Not Overlapped with Data Readout Mode

Most sensors uses this mode when input trigger is active.
This mode gives lower fps value than Exposure Overlapped with Data Readout mode.

exposure_not_overlapped
Sensor timing in Exposure Not Overlapped with Data Readout Mode
In this mode the timing depends on sum of:

  • Input transition time (t itr) depends on:
  • Digital Input Delay - time for changing internal circuit to active state. It is constant for each camera model
  • Input Debouncing Time - time for stabilizing uneven input signals (e.g. from mechanical switches). This time can be can be set using xiAPI with parameters XI_PRM_DEBOUNCE_EN and XI_PRM_DEBOUNCE_T0 on some cameras. Default 0.
  • Exposure time (see ET above).
  • Data Readout time (see t rd above)

Table1: Typical times for selected camera models

Camera Model DownS t itr [µs] t exp [µs] t eio[µs] t expo[µs] t rd[µs] Notes
MU9 models:
MU9 any 200+
xiQ/MQ models:
MQ013xG-E2 any 1.4 29 19/238 -10 400+16.4*BWF*LC N1, N2
CURRERA-R - OC models:
RL13-OC any 0.1 42 18 0 400+16.4*LC
RL50-OC 1 0.1 2 0.3 0 2000+37.7*LC
RL50-OC 2 0.1 2 0.3 0 2000+32.4*LC
RL50-OC 4 0.1 2 0.3 0 2000+46.1*LC
RL04-OC 1 0.1 11 11 0 1500+36.8*LC
RL04-OC 2 0.1 11 11 0 800+35.8*LC
RL04-OC 4 0.1 11 11 0 680+40.1*LC
CURRERA-R - 24V models:
RL13-24 any 0.1 109/18 127/36 0 400+16.4*LC
RL50-24 1 0.1 109/18 109/18 0 2000+37.7*LC
RL04-24 1 0.1 109/18 127/36 0 1500+36.8*LC

Note N1: V(Input)=15V
Note N2x in model name means all available models (M, C, R)

Table1 column names:
DownS = Current camera DownSampling (XI_PRM_DOWNSAMPLING)
eio = Trigger (Digital Input) to Strobe (Digital Output) (on some models is listed: Off->On change / On->Off change)
exp = Strobe (Sensor) to Digital Output (on some models is listed: Off->On change / On->Off change)
expo = Start of exposition to Exposure Active Digital Output
LC = Current Line Count (XI_PRM_ HEIGHT)
BWF = Bandwidth Factor for maximum bandwith this is 1 when the bandwith will be lower BWF will rise (TBD)
exps = Current Exposure Time set (XI_PRM_EXPOSURE)
Conditions: XI_PRM_DEBOUNCE_EN=0 (off).
__

Minimum trigger period (Ttrig_min)

Minimum trigger period can be calculated using the following formula:

  • trig_min = t exp + t exps + t rd

Example for MQ013MG-E2, Exposure time = 500us, image = 500 pixels width x 200 pixels height.

  • trig_min = 29µs + 500µs + 400µs + 16.6µs * 200lines = 4249µs

Triggered mode with overlap

Several sensors are capable to trigger exposure in overlap mode, so it is capable to reach the same fps value as in free run mode.

When trigger period is longer than exposure and readout the signal wave form will look similar to Trigger mode without overlap.

However, when the trigger period will decrease sensor will expose images in overlap mode.
In this case frame active signal will be all the time active.

Sensor timing in Exposure Overlapped with Data Readout Mode
For timing description please see previous paragraph Triggered mode without overlap

Table2: Typical times for selected camera models

Camera Model DownS t itr[µs] t exp[µs] teio[µs] texpo[µs] t rd[µs] Notes
xiQ/MQ models:
MQ042xG-CM any 1.4 10 11/224 0 (64.5+5.375*LC)*BWF N1,N2
MQ022xG-CM any 1.4 10 11/224 0 (37.625+5.375*LC)*BWF N1,N2
MQ003xG-CM any 1.4 10 11/224 0 (90.7 + 3.78 * LC)*BWF N1,N2,N3
MQ013xG-ON any 1.4 <2 11/224 0 (23*W+3300)/BW+(7.66*W+1106)*LC/BW N1,N2

Note N1: V(Input)=15V
Note N2: 8bit per pixel maximum bandwidth (TBD)
Note N3: for t exps > t rd t eio is in table; for t exps < t rd t eio is t eio in table plus (t rd-t exp) approximately

Table2 column names:

DownS = Current camera DownSampling (XI_PRM_DOWNSAMPLING)
eio = Trigger (Digital Input) to Strobe (Digital Output) (on some models is listed: Off->On change / On->Off change)
exp = Strobe (Sensor) to Digital Output (on some models is listed: Off->On change / On->Off change)
expo = Start of exposition to Exposure Active Digital Output
W = Image width(XI_PRM_WIDTH)
LC = Current Line Count (XI_PRM_ HEIGHT)
BW = Bandwidth in Mbit/s
BWF = Bandwidth Factor see table below
exps = Current Exposure Time set (XI_PRM_EXPOSURE)
Conditions: XI_PRM_DEBOUNCE_EN=0 (off).

Bandwidth factor

Bandwidth factor is number reflecting the ratio between maximum sensor frequency and current sensor frequency calculated from Bandwidth Limit.

BWF = F max / F limit
Where F max is maximum possible clock for used sensor in MHz and F limit is used clock depending on Bandwidth Limit parameter set in API (XI_PRM_LIMIT_BANDWIDTH). F limit is set in 1MHz steps and can not go lower than F min.

 

MQ042xG-CM MQ022xG-CM
max = 48MHz
min = 5Mhz
limit = ((129*BW)/(8192*BPP))*((12+LC)/LC) [MHz]
fot = 64.5*BWF [us]
BPP - number of bytes per pixel
BW - bandwidth in Mbit/s

 

MQ042xG-CM-SR2 MQ022xG-CM-SR2
max = 48MHz
min = 20Mhz
limit = ((129*BWL)/(8192*BPP))*((12+LC)/LC) [MHz]
fot = 64.5*BWF [us]
BPP - number of bytes per pixel
BWL - bandwidth limit in Mbit/s

 

MQ003xG-CM
max = 43 MHz
min = 38 MHz
lim = ((325*BWL*)/(2529792*BPP))*(13+LC/2) [MHz]
lim - must be rounded down to the nearest whole number and must be in the range <F min , F max>

BPP - number of bytes per pixel
BWL - bandwidth limit in Mbit/s

Minimum trigger period (t trig_min )

Minimum trigger period can be calculated using the following formula:

  • trig_min = t exp + t exps (When exposure time is longer than readout time)
  • trig_min = t rd (When exposure time is significantly shorter then readout time)
  • trig_min = t exps + t fot (When exposure is smaller than readout time but the difference is less than t fot )

Example for MQ022MG-CM, Exposure time = 500us, image = 2048 pixels width x 1088 pixels height with maximum bandwidth and 1 byte per pixel.

  • trig_min = 10µs + (37.625+5.375*1088lines) * 1 = 5895µs