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DLP5531-Q1: DLP5531-Q1

Part Number: DLP5531-Q1

Dear specialists!

We are developing now an illumination system using Texas Instruments's model DLP5531.

And we have a pair of questions.

1. Do we understand right that for incident spot angular divergence in transversal direction is not limited?

Can we use a spot with the next divergence: +/- 12 deg (longitudinal), +/- 35 deg (transversal)?

2.  The efficiency 66% was specified for the angle of incidence: 24 deg (longitudinal), 0 deg (transversal).

What will be efficiency for the other angles of incidence:

Point 2. -36 deg (longitudinal), 0 deg (transversal)?

Point 3. -24 deg (longitudinal), 35 deg (transversal)?

Point 4. -36 deg (longitudinal), 35 deg (transversal)?

You may see the corresponding picture with comments using the next link (google photos):

Thank you in advance!

  • Hello,

    Let me start by responding to the image that you provided. It looks like there is some missing and some incorrect information in the diagram. In your diagram the output at 24° should be the flat state light (light that is reflected off of the DMD window and other surfaces). Then you should have the off state light at 48°. Here is a diagram from an application note on DLP System Optics:

    This is from the DLP System Optics Application Report. The report is focused on consumer applications rather than automotive but it provides a lot of good information and background on DLP systems in general.

    To answer question #1:

    Yes you can have different cone angles in the horizontal (transverse) and vertical (longitudinal) direction. However as you increase the cone angle you will see a reduction in contrast. This is because light diffracted by the DMD will begin to overlap the on state light and be captured by the projection optics. This means there is a trade off between how large a cone angle (how small an f-number) you can use and the achievable system contrast. Without knowing what is acceptable for your system I couldn't really say whether or not your proposal would be acceptable.

    To answer question #2:

    The 66% efficiency is based on the following assumption noted in the datasheet:

    DMD efficiency is measured photopically under the following conditions: 24° illumination angle, F/2.4 illumination and collection
    apertures, uniform source spectrum (halogen), uniform pupil illumination, the optical system is telecentric at the DMD, and the efficiency
    numbers are measured with 100% electronic micromirror landed duty-cycle and do not include system optical efficiency or overfill loss.
    This number is measured under conditions described above and deviations from these specified conditions could result in a different
    efficiency value in a different optical system. The factors that can influence the DMD efficiency related to system application include:
    light source spectral distribution and diffraction efficiency at those wavelengths (especially with discrete light sources such as LEDs or
    lasers), and illumination and collection apertures (F/#) and diffraction efficiency.

    We calculate the efficiency based on whole illumination bundle not at a single point. For more information on how we calculate DMD efficiency we will be releasing an application note on later this year.

  • Dear Jake, thank you very much for your answer.
    Let me ask one more.

    Question 1. Can you explain more about the flat state? Why should we consider the flat state? Does flat state takes some significant time while it is switching ON-OFF?
    I mean what if we use wider spot (48 deg: -12..-60 and it be reflected into -12 ..+36 in the ON state (and there we try to collect this beam by the projection lens) and in the OFF state the beam be reflected to +36..+84. The flat state (+12..+60) will cross both ON and OFF states. But what the matter with it?

    Question 2. Can you share any known information about decreasing of effeciency for higher angle of incidence? For any wavelength.

    In our case we use white LEDs. But I would be happy to collect any information for preliminary and rough estimation.

    Thank you.
    Sorry for bothering.
  • Georgy,

    No a bother at all. In regards to questions #1, flat state light doesn't refer to the light reflected off of the mirrors. You're correct that the mirror switches very quickly. The light we are referring to is anything that's reflecting off of the window, package, or other elements of the DMD that are normal to the projection optics. If that light is captured by the projection optics it will impact your contrast. This is why you don't want the flat state cone to overlap the on state cone.

    For question 2 I reached out to you directly via email with some preliminary information. We will have a full app note on this topic on later this year.

    Best Regards,

    Jake Pulliam