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Original question:

DLPDLCR4710EVM-G2: dlpdlcr4710evm-g2 pattern storage

DLPDLCR4710EVM-G2: Background Blinking of Patterns When Shining with Femtosecond Laser

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Genius 9830 points
Part Number: DLPDLCR4710EVM-G2
Other Parts Discussed in Thread: DLP4710EVM-LC

Dear  experts,

I use the chipset in DLPDLCR4710EVM-G2 as a spatial light modulator to shape a femtosecond laser (1 kHz, 100 fs, 400 nm). The input to the EVM is a 1-bit depth binary image, a ring pattern, through the HDMI port. I succeeded to see the ring pattern, but there is a blinking background at some frequency which is not desirable for my application. Do you have any solutions to remove the background? Thank you very much.

Best Regards,
William

  • 0
    TI__Expert 6620 points

    Hello User,

    Can you share what frame rate that your image source is sending this image at?

    This could be a case where the laser is still projecting onto the DMD while it is resetting between VSYNCs from your image source. You would need to stop the laser from projecting before the next VSYNC signal is received. The data sheet here, page 20 section 6.11 shows the transition timings for the DMD.

    The DLP4710EVM-LC would have more control over something like this use case. There are triggers that can be used to signal external hardware when the EVMs is going to project content. There is more control over monochrome patterns including pre/post and exposure times. It would be feasible to sink the laser to the EVM.

    Regards,
    John 

  • 0 in reply to John McKnight
    TI__Genius 9830 points

    Dear John，

    Since the display input is through the HDMI port connecting to my laptop, the frame rate is 60 Hz. Are you suggesting to block the laser beam during the mirror switching time, such as using a chopper, to avoid the blinking of projection? Is there any other solutions? Because I would like to see a static image of the patterned laser beam for my application. Thank you!

    Best Regards,
    William

  • 0 in reply to Links
    TI__Expert 6620 points

    Hello William,

    The DMD will always have to reset for the next VYSNC whether the image is static or not. The only way to work around it is to block the laser or stop the laser itself.

    Do you have a desired exposure time that you need to meet for you application?

    The light control chipset would allow for a trigger signal to sync cameras/ peripherals with the image projection from the EVM. 

    Regards,

    John

  • 0 in reply to John McKnight
    TI__Genius 9830 points

    Dear John，

    The longest desired exposure time for my application is around 60 s. I've noticed that the mirrors need to be reset to prevent them sticking at one position by checking out the E2E forum. I would like the projection to be like a static image, i.e., without all the background blinking. Is there any chance that I can achieve that through programming or physically block the reset signal via hardware extension like shown in this paper arxiv.org/.../1611.03397 ? Also, I noticed that the blinking frequency is different when I use different laptops to control the DMD. Thank you.'

    Best Regards,
    William

  • 0 in reply to Links
    TI__Genius 11210 points

    Hello William,

    Thanks for your reply!

    We cannot say if the hardware extension you shared would work since we don't test. 

    Like John said the light control chipset would allow for a trigger signal. For more information, please refer to the DLP Pico FAQ here: https://e2e.ti.com/support/dlp-products-group/dlp/f/dlp-products-forum/946506/faq-dlp-pico-universal-faq

    Regards,

    Lori