Ranger Camera Configuration : SICK Ranger E example

Here are the steps to configure the camera for a given field of view and belt speed.

To illustrate with realistic values we will follow a case study with a Field of view (FOV) of 600 mm and a belt speed of 2,2 m/s.

Pulse triggering using an encoder

In order to have the same resolution in the belt direction than perpendicular we have to acquire at 2200(mm/s) / 0, 4(mm) = 5500Hz (cycle time = 181 µs).

So we could acquire 'free-running' with trig mode = 0 and cycle time = 181 µs or use an encoder to keep object proportion when the conveyor speed may vary.

We chose an encoder like the DFV60 providing 65536 pulses by revolution. In this case one revolution correspond to 300mm and the camera receive one pulse each 300/65536 = 0,0045 mm. As we need to trig one line each 0,4mm, we specify the parameter pulse per trig = 0,4/0,0045 = 87.

Exposure versus cycle time

In free-run mode  (trig mode = 0) the exposure can be equal to the cycle time for the best performences.

In pulse triggering mode (trig mode = 5 for motion mode) a reset time has to be added with reset + exposure <= cycle time.

The time it takes to reset the sensor rows within a ROI is equal to the shortest possible exposure time for the ROI. For short exposure time it could be significant.

In our case with an ROI of 128 lignes and the cycle time of 183 µs the reset time is 71µs and the exposure is 112 µs ! We have to chose to loose 71µs of exposure to be sure that the belt speed remain constant !

Pixel resolution : 

Horizontal max and threshold : 1/2 pixel resolution
Horizontal threshold : 1/2 pixel resolution (1 thres), 1/4 pixel resolution (2 thres)
Horizontal max : 1 pixel resolution (), 1/2 pixel resolution ()
Hi-resolution 3D : 1/16th pixel resolution

Acquisition direction
Specifies whether to start at the bottom or the top of the ROI when searching for the laser line. Default: 0.
0 = Start at bottom
1 = Start at top

Range axis 
Specifies whether to measure the range from the bottom or the top of the ROI, depending on the acquisition direction.

Range Axis = 0, Acq Dir = 0 : Highest value at top of the ROI
Range Axis = 0, Acq Dir = 1 : Highest value at bottom of the ROI
Range Axis = 1, Acq Dir = 0 : Highest value at bottom of the ROI
Range Axis = 0, Acq Dir = 0 : Highest value at top of the ROI

ROI = Row 0 : top, Row bottom : 512

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