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DLP670S: Does TI utilize blaze condition in designing DLP projectors ?

Minjae Kim
Prodigy 10 points
Part Number: DLP670S

Tool/software:

Dear Texas Instruments Team,

Hello, I am currently developing a DLP-based 3D printer using the DLP670S chipset.

Since the DLP670S has a micromirror tilt angle of 17.5°, I have been illuminating the DMD with 405 nm UV light at a 35° incident angle, so that the reflected beam travels in the direction of the DMD surface normal.

While researching this setup, I came across the paper “Maximizing energy utilization in DMD-based projection lithography,” which suggests that the highest energy efficiency does not necessarily occur when the incident angle is twice the mirror tilt angle. Instead, the authors define a condition called the “blaze condition” that leads to maximum diffraction efficiency.

Based on this paper, I implemented a simulation and observed that the maximum efficiency occurs at an incident angle of approximately 46°, rather than at 35°.

This leads me to the following question:
Does Texas Instruments always consider and utilize the blaze condition when designing DLP projectors?

If not, could you please share the reason why this condition might be intentionally avoided or not prioritized?

Thank you very much for your time and support.

Best regards,
Minjae Kim

  • 0
    TI__Guru 54320 points

    Hello Minjae,

    Not specifically.  Since blaze is wavelength specific for a given pixel pitch we do not design to a specific wavelength.  TI builds a number of DMDs with different pixel pitches.  Not everyone wants to design with the same wavelength.  

    It is not feasible to build DMDs with every possible combination of wavelength, pixel pitch and tilt angle (i.e. blaze).

    Fizix

  • 0 in reply to Fizix
    Prodigy 10 points

    Thank you for your quick response, Fizix.

    In that case, is it correct to say that — for convenience — the incident angle is often set to twice the mirror tilt angle, even if this results in an anti-blaze condition, and the system is instead designed to ensure that the four brightest central diffraction orders all enter the projection lens?

  • 0 in reply to Minjae Kim
    TI__Guru 54320 points

    Hello again Minjae,

    Many DMD applications do no use coherent light, but rather broadband.  The typical condition is for the incident angle to be twice the mirror tilt angle so that the projection angle is normal to the DMD window.  This indeed may potentially result in and anti-blaze condition, but can be anywhere between a blaze or an anti-blaze.  

    Also the tilt angle is +/- 1 degree, and can vary across the DMD.

    Fizix