Calculating motion rate for given line scan rate

[M0Reng]

Dear friends,

I need to understand the calculation of motion rate for given line scan rate.

i have line-scan camera connected to servo motor.

i know that the line-scan camera can run at 7.2 khz line rate (7200 lines in 1 second).

Each pixel need to be 0.1mm (in the direction of motion). 10 lines of scanning is 1mm.

i need to scan image of object that its length is 400mm (0.1mm*4000lines)

First, the Conveyor stop, the object that i need to test with the linescan camera is now 5cm from the camera.

i want that the servo motor will move the conveyor for 45cm and stop. 

(the conveyor accellerate, move const speed, decellerate, stop. the line scan camera connected to 10khz encoder for each revolution)

Now i'm getting lost with the calculation.....

if 1pixel = 0.1mm , then i need the conveyor belt be able to move 0.1mm for each pulse of the encoder???

i want that the servo motor will rotate chain (like the attached image),

but i dont know how i need to calculate the gear diameter, the chain pitch, etc...

and specially, how this parameters influence the line scan rate, and what is the role of the encoder here...

Thanks for any support.

Moti 

[BruceAmmons]

It sounds like you are mixing two methods of using a line scan camera.

The first method is to run the camera at a fixed speed.  If the speed of your belt is constant, this can work okay.  To calculate the desired speed, let B=belt speed (mm/sec), L=line rate (lines/sec), R=mm/line (0.1mm/line in your case)

B = L / R    This equation can be rearranged to calculate any of the quantities.

The second method is to use an encoder to trigger each line captured by the camera.  In this case, the speed of the belt is not important as long as you don't go too fast for the camera.  In this case, you need to know how many mm the belt will travel for each pulse.  To calculate this, you would probably measure how far the belt travels during one revolution of the encoder.  You should also know the number of encoder pulses per revolution.  Dividing distance by pulses gives you distance per pulse.  Since you want 0.1 mm/pulse, you would need to adjust either the number of pulses in the encoder or the diameter of the belt roller.  If E=encoder pulses and D=belt distance, R = D / E.

Bruce

[M0Reng]

Dear Bruce,

Now i know why i mix all things together....

i want the second option : to use an encoder to trigger each line captured by the camera.

your calculation and the explanation is very clear to me.  

Thank you very much! 

Moti

[Fritz2]

MOReng,

I found something very helpful in the internet, weher you can interactively calculate necessary parameters for line scan cameras.

Could that help?

Try this:

http://www.vision-doctor.co.uk/camera-calculations/calculation-line-scan-frequency.html

What is your opinion?