Nota
Ulteriori informazioni sull’implementazione inclusi gli esempi di software sono riportati di seguito nel paragrafo Temi applicati.
Nella verifica della qualità delle superfici contano il riconoscimento di scostamenti di forma non tollerabili e di strutture definite. Per eseguire entrambe le attività in tempi brevi e con robustezza sufficiente, si raccomanda di illuminare i componenti da diverse direzioni e di acquisire ed elaborare le immagini delle ombre risultanti. Tale principio prende il nome di “Shape-from-Shading” (SfS).
Le telecamere CX.I sono dotate di quattro uscite di potenza commutabili separatamente con modulazione della larghezza degli impulsi e una potenza di uscita fino a 120 W (max 48 V / 2,5 A). In combinazione con il sequencer, queste quattro uscite consentono una semplice realizzazione di un controllo luce del quadrante per Shape-from-Shading.
Le quattro uscite della telecamera devono essere impostate sui quadranti corrispondenti dell’illuminazione. Al fine di prevenire errore occorre configurare le stesse impostazioni per tutti e quattro i quadranti.
Nota
Attenersi alle avvertenze generali per la messa in servizio, la massima portata e la configurazione degli output nel manuale d’uso della telecamera (UsersGuide_VCXG_.I.XT_VCXU_vxx_xxxxxx.pdf).
Gli ultimi software e le documentazioni tecniche sono disponibili su: vt.baumer.com
Per Shape-from-Shading la telecamera viene commutata alla modalità trigger. Successivamente, ad ogni segnale trigger in ingresso vengono acquisite quattro immagini.
Per ogni immagine acquisita, le uscite della telecamera attivano l’illuminazione ad anello di un quadrante.
Camera behavior for shape from shading
Timing diagram for shape from shading
The Sequencer configuration for shape from shading is as in the example below, taking into account the basic sequencer principles.
o first sequencer set to activate illumination upon start of exposure
o second sequencer set to switch off illumination at the end of exposure
As the sequence needs to be started by a trigger, a TriggerSource must be defined. In this example, this is Line0. The trigger signal enters via this source.
Outputs/Illumination control
Camera mapping of the individual output status (Lines) is binary while parameter configuration is in hexadecimal format.
| Line 7 | Line 6 | Line 5 | Line 4 | Binary value | UserOutputValue (hex value) |
All Lines OFF | 0 | 0 | 0 | 0 | 0000 | 0 |
Line4 ON, other Lines OFF | 0 | 0 | 0 | 1 | 0001 | 1 |
Line5 ON, other Lines OFF | 0 | 0 | 1 | 0 | 0010 | 2 |
Line6 ON, other Lines OFF | 0 | 1 | 0 | 0 | 0100 | 4 |
Line7 ON, other Lines OFF | 1 | 0 | 0 | 0 | 1000 | 8 |
All Lines ON | 1 | 1 | 1 | 1 | 1111 | F |
Sequencer set 0
The first sequencer set is the idle set. At this point, the camera is waiting for the incoming trigger and the illumination is deactivated (UserOutput Value = 0). The rising edge of the trigger signal is used to start the first exposure and switch to the second sequencer set.
Sequencer set 1
In the second sequencer set, TriggerMode is deactivated. The rising edge of the ExposureActive signal relating to the first image is used to switch to the next sequencer set.
Sequencer set 2
This sequencer set has Line4 output activated meaning the illumination of quadrant A is active. (UserOutputValue is set to 1.) The falling edge of the ExposureActive signal relating to the first image is used to switch to the next sequencer set.
Sequencer set 3
This sequencer set will deactivate the quadrant A illumination at the end of the first exposure.
Sequencer set 4
In this sequencer set, the Line5 output is activated, which means that the illumination for quadrant B is also activated. (UserOutputValue is set to 2.) The falling edge of the ExposureActive signal relating to the second image is used to switch to the next sequencer set.
Sequencer set 5
In this sequencer set, the illumination for quadrant B is deactivated at the end of the second exposure.
Sequencer set 6
In this sequencer set, the Line6 output is activated, which means that the illumination for quadrant C is also activated. (UserOutputValue is set to 4.) The falling edge of the ExposureActive signal relating to the third image is used to switch to the next sequencer set.
Sequencer set 7
In this sequencer set, the illumination for quadrant C is deactivated at the end of the third exposure.
Sequencer set 8
In the last sequencer set, the Line7 output is activated, which means that the illumination for quadrant D is also activated. (UserOutputValue is set to 8.) The falling edge of the ExposureActive signal relating to the fourth image is used to switch to sequencer set 0.
One after another, the four acquired images of the inspected object are transmitted to a computer where they are composed to form a single image. This image serves for surface quality inspection by showing any form or structure incompliance.
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