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Time for capture image in low light

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  • Time for capture image in low light

    Hi Kevin,

    We are using the uCAM-III during night time using an infrared lighting source (940nm) using batteries. In order to reduce power usage is it possible to switch the IR lighting source on, take a snap shot (one data frame) using the getpic command and then turn off the IR lighting source? During the off time the frame is transferred to the host (Atmel SAMD21) over a dedicated serial line.

    The uCAM-III coms setup is 921600, and 8 bit gray scale, RAW mode 60x80 or 128x96.
    Images are captured every 0.5 second at 60x80

    From previous data sheet the total time (Ttotal) the image is captured and sent is Ttotal =Tframe + Tshutter.
    where Tframe is the time to transfer one data frame of image (header and payload) from uCAM-III to the host
    and Tshutter is the time after getpic starts to be sent before image processing begins (Datasheet specs a range between 150 and 200ms)

    How does the uCAM-III process the image exposure/brightness/contrast to capture the frame into memory? Is it only during Tshutter time when getpic received from host or during Tshutter and Tframe, or processes it in the background ie any time the uCAM-III is ON?
    The images are in low light so may need some time for processing.

    Regards
    Gerald





  • #2
    Hi Gerald,

    In order to reduce power usage is it possible to switch the IR lighting source on, take a snap shot (one data frame) using the getpic command and then turn off the IR lighting source?
    Yes, it should be possible.

    Images are captured every 0.5 second at 60x80
    If you are planning to capture an image for every 0.5 seconds, I think you should also consider the rising and falling time of your IR light.
    However, if the time is minuscule, it should be fine.

    One thing that I would suggest is for you to conduct testing (trial and error) in order to maximize the efficiency of saving power.
    You could try to switch the IR for around 150 ms after sending the Get Picture command, turn it off after 100 ms, and check the image.
    If you get a nice viewing image, you could play and adjust the time for how long the IR would stay on.

    Best Regards,
    Kevin
    Last edited by John Kevin; 18 June 2019, 04:42 PM.

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    • #3
      Hi Kevin,

      Thanks for the feedback,Will try out


      Regards
      Gerald

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