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Maximum Internal Pattern Rate

hai jiao
Prodigy 110 points
Other Parts Discussed in Thread: DLPC300

hello,

I am new to lightcrafter, in the user’s guide there is an equation
regarding to internal pattern rate, where it said Pattern Rate = (1/Pattern
Exposure Period) + (Bit Plane Load Time) + (Buffer Rotate Overhead),
I find this equation quite wrong, because on the right hand side, I believe the
unit is in Hz, but the left hand side is Hz plus time. Currently I want to achieve
2880 fps of bit plain structured light patterns, with typical bit plane load
time = 230µs and buffer rotate overhead = 135µs, if the equation above was
indeed “Pattern Rate = 1/(Pattern Exposure Period + Bit Plane Load Time + Buffer
Rotate Overhead)” the maximum pattern rate I can get is 1/(250 + 230 + 135)us =
1626Hz, this is quite contradictory to Table 3-2 in the user guide of 4000Hz, monochrome,
1 bit per pixel, 96patterns. Can someone tell me where I am wrong?

hai

  • 0
    TI__Prodigy 410 points

    Hello Hai,

    The 4000Hz can be achieved only on the following conditions.

    For 1 bit patterns the Bit Plane Load time and Exposure period can be overlapped, provided you set the exposure time to 0

    If the number of patterns are within 24 then the Buffer Rotate overhead does not come into account.

    ie.

    Bit Depth = 1

    Number of Patterns <= 24

    Exposure Time = 0

    Period = 250

    Regarding your first question about the equation, yes, there is a typo in the usage of braces.

    The correct equation is:

    Pattern Rate = 1/((Exposure Time) + (Bit Plane Load Time) +( Buffer Rotate Overhead))

  • 0 in reply to Sureshkumar Manimuthu
    Prodigy 110 points

    Wow,

    Thank you very much Sureshkumar, I didn’t expected
    anyone would give me a reply this fast!

    Hai

  • 0 in reply to hai jiao
    TI__Expert 6995 points

    Hai,

    See this posting for a little more information. We are reviewing an update on the DLPC300 SW Programmer's Guide that explains how to program the DLPC300 for these speeds. We will post it as soon as we complete our review.

  • 0 in reply to Sureshkumar Manimuthu
    Intellectual 445 points
    Hey,

    There are two options in the Timing tab of the GUI. The first one is called Pattern Exposure(us) which is the amount of time for which a pattern will be displayed and the second one is called Pattern Period(us), this the interval between two subsequent patterns.

    Now, I am using DLP LightCrafter 4500 and in that, Patten Exposure cannot be less than 235us and the difference between Pattern Period - Patten Exposure cannot be below 230 us. So I don't know what do you mean by exposure time = 0.

    Now, I am playing a sequence of 24 1-bit images stored in flash. My Pattern Exposure is 235us and Pattern Period is 235us. I am using only one buffer so, Buffer Rotate Overhead is not valid. Now, if I put my values in the formula you have mentioned for the Pattern Rate I get 2127.65 Hz.

    Pattern Rate = 1/((Exposure Time = 235) + (Bit Plane Load Time = 235) +( Buffer Rotate Overhead = 0)),
    Therefore, Pattern Rate = 2127.65.

    So how are you saying that DLP LightCrafter can project pre-loaded patterns at 4KHz. Kindly explain.

    Thanks,
    Aamir