• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 28 subscribers
  • Views 778 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DLP4500: Why images have slight different despite the brightness when the pattern exposure time is doubled ?

ws
Prodigy 115 points
Part Number: DLP4500
Other Parts Discussed in Thread: DLPC350

I am using the pattern sequence [variable exposure] mode to project a fringe image with bit depth of 7 bit. The minimum pattern exposure period is 4500 us. However, the fringe image that i obtained is not smooth thus i increase the exposure time to 9000 us which is double of the minimum exposure time and i get  . I am expecting two similar images with different brightness.  Please check the attachment for the images.

Is the bit pattern built as described in this thread? https://e2e.ti.com/support/dlp/f/94/t/594673

If so, why the two images are different despite the brightness?

Thanks in advance

  • 0
    TI__Genius 10925 points

    Hi Weiseong, 

    Welcome to TI E2E Forums! Could you kindly provide us the INI settings of both your configuration and the image used? This will help us reproduce your problem at our end and debug faster!

    Thanks & Regards,

    Hirak.

  • 0 in reply to Hirak Biswas
    Prodigy 115 points

    Hi,

    Sorry for the late reply. I attached the bin file together with the ini file and the image. After you read the settings at the pattern sequence [variable exposure mode], the first setting with exposure time 4500us will project the fringe image at the left hand side from the image i attached before. The second setting with exposure time 9000us will project the right hand side image. 

    Thanks.

    reference.ini

  • 0 in reply to Hirak Biswas
    Prodigy 115 points

    Hi,

    I am new to here and might miss out the functionality to attach proper image format and the bin file. So, i will share those file in the google drive below. 

    https://drive.google.com/open?id=1lAExS1Y6r1Y3SA6f6atkmBaaOquFp668

    Thanks,

  • 0 in reply to ws
    TI__Genius 10925 points

    Hi,

    Thanks for your patience! We looked into your issue and found that we could not spot a difference with naked eyes. HOWEVER, that doesn't mean it is not there. SInce you are using pattern sequence mode, all the internal image improvement functionality of DLPC350 is disabled. This causes difference in displayed image under different exposure lengths. Since the selected bitplanes are being displayed in a simple binary bitweighted fashion, changing the length of the sequence (i.e., the pattern sequence exposure time) can introduce some unexpected artifacts in the visible image. This has more to do with how the displayed bitplanes are integrated into one image by the camera/our eyes, and is not a defect in the displayed bitplanes. In video mode, we make some adjustments in the bitplanes and also in the way the bitplanes are shown, so the artifacts are not visible to human eyes anymore, but also in this case the displayed image is not pixel accurate WRT the input images. In the pattern sequence mode we have to disable all kinds of adjustments to make the displayed image pixel accurate WRT the input images.

    Hope this helps. 

    Thanks & Regards,

    Hirak.

  • 0 in reply to Hirak Biswas
    Prodigy 115 points

    Hi Hirak,

    Thanks for your reply. So, if I want to play around with the exposure time, I should change the exposure time based on the multiple of the minimum exposure time or just exceed the minimum exposure time? 

    Thanks. 

  • 0 in reply to ws
    TI__Genius 10925 points

    Hi Weiseong, 

    To comment on that, I need to know more about your specific application. What do you aim to achieve by varying the exposure time of bitplanes?

    Thanks & Regards,

    Hirak.

  • 0 in reply to Hirak Biswas
    Prodigy 115 points

    Hi Hirak,

    The application is just to increase the brightness with the correct images projected without changing the LED current. Based on my understanding, the minimum exposure time is the time needed to complete the one projection of certain bit depth image. So if i change the exposure time but not the multiple of the minimum exposure time, the image that i get might be for example one and a half projection. Correct me if I am wrong.

    Thank you for your reply.

  • 0 in reply to ws
    TI__Genius 10925 points

    Closed due to duplication,. 

    Thanks & Regards,

    Hirak.