help image acquisition only when light is on

[deveron]

Hi, i need help to create an instrument.

i have to create an instrument to do:

i have a black box with a camera. this camera will be connected via USB to the pc. When i press a pedal a strong light comes througt it.

i need that labview shows a real time image when the light comes in and stops showing the image when the light comes out, showing the last frame that had light. it is like a system called last image hold.

for example:

i have a pedal that start a high light. LV does not show any image, when i press the pedal and light comes in, LV stars to show the image, when i stop pressing the button LV shows the last image or frame that had light. If it start another time to press the pedal LV start to show the new images until i stop to press the pedal.

any idea?????

thanks

Jorge

[Hatef.fouladi]

two way to do this 

one use hardware solution (trigger for camera ) this trigger could come from  one photocell that measure the light and give comment to acquire it is best way for  fast vision project 

second  use one case structure in your program and the code for make true of this program should be with bellow algorithm

use IMAQ Light Meter (Rectangle) VI  select your ROI and give threshold for light to compare with light  measured by this vi .based on your experiment analyses you have to select value of threshold  (max allowed  threshold is 255) . ok when your IMAQ Light Meter value overflow the threshold value the compare operator  return true just wire this to your case structure and put your image display icon  inside true frame

it is best way for low speed computer vision and just work up to 33 ms actions

[deveron]

Thanks i will try with case structure and come back to tell if i could managed it.

thanks!!!!!

[Hatef.fouladi]

feel free if you need example code

[deveron]

I have done as well as i could, but i am not getting the histogram nor gray levels of the ROI...

please take a look to the image attached.

anyway maybe an example code could be more helpful.

thanks

[Hatef.fouladi · Accepted solution]

use this it will be help you