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DLP not projecting exact 8 bit patterns

Mira Sibai
Prodigy 35 points
Other Parts Discussed in Thread: DLP5500, DLPC200

hi,

I have the DLP 5500 connected to an external light source. I have created 8 bit gray scale patterned images (sinusoidal) to be projected on a sample.

Recently I have noticed problems with my DLP projecting true gray scale patterns. I am using the PD logic DLP control software to import 8 bit patterned images. I have noticed that the patterns coming out of the DLP are not exactly 8 bit; I see dark lines in between one shade and another in the same image and these lines will change according to LED illumination time. Note that I am not using the LEDs connected to the DLP, but rather have a Lumencore light source (other LEDs) connected. I cannot disable this. I project one pattern and capture it with 14 bit CCD. I have tried syncing with an external 3V  source, but still get the same effect. I have played with the frame rate as well and the software sometimes does not allow for high frame rate even though I choose frequencies below the maximum allowed frequency. Would you know what is happening and why I get the lines in between gray intensities? What can I do? Help please!

  • 0
    TI__Mastermind 30875 points

    Hello Mira,

    The DLP5500 platform uses both DMD and Illumination module to generate the linear grayscale intensities.

    If you look at the hardware setup for each LED there are two basic controls going from DLPC200 to the LED DRIVER a) LED_EN  strobes b) LED_Current (on Logic H/W this info is sent via SPI master slave interface) 

    For a different ILLUMINATION MODULE like in your case, while (b) is not important i.e., you can determine max drive current strength according to your interest;  (a) is a MUST. The illumination module should respond (turn ON/OFF) as per the LED_EN signals, failing which produce wrong intensities.

    For experiment, base on the LED selection probe the LED_EN signal notice how it is modulating over pattern display time.

    Let me know if this answers your question.

    Regards,

    Sanjeev