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DLP7000: About definition of screen lumens

Leonardo0131
Intellectual 480 points
Part Number: DLP7000

Hi

I have a question about the screen lumens.

Is the screen lumens reflected by the DMD mirror and leaving the window?
What part of the light is called the screen lumens?

Please let me know the documentation that explains the screen lumens.

Best regards

Leonardo

  • 0
    TI__Guru 54705 points
    Hello Leonardo,

    This considered a "term of art" in the projector industry. It is the lumens as measured at the projection screen, so it depends what is coming out of the DMD/projection lens.

    A similar term is "ANSI lumens" which is a method of measuring lumens at a projector screen that has been standardized by ANSI.

    Searching for "ANSI lumens" in your browser will give you many useful (an probably some not so useful) results.

    Fizix
  • 0 in reply to Fizix
    Intellectual 480 points

    Fizix-san, 

    Thank you for your support always. 

    I got the additional questions about the screen lumen from customer.

    Where does the screen lumen mean the light?

    ①：Light on the DMD

    ②：Light exiting the DMD

    Best Regards,

    Leonardo

  • 0 in reply to Leonardo0131
    TI__Guru 54705 points

    Hello Leonardo,

    The answer is #2 (sort of).  Typically it is actually measured at the screen in several points (average luminous flux [ illuminance ] coming to the screen x the area).

    Let's use an example for a given projector:

    • Suppose a screen is at 5 m and has an average luminous flux of say 200 lm/m^2 and a projected area of 5 m^2..  Then the total output from the projector is 200 lm/m^2 x 5 m^2  which gives 1000 lumens.
    • Now suppowe we move the screen out to 10 m distance.  Since the distance is doubled, both the x & y dimension of the screen are doubled so that the area is quadrupled (4 x).  The projected area is now 20 m^2.  But the light is also spread out by the same factor and the average luminous flux goes down by a factor of 4 to 50 lm/m^2.  Then the total output is 50 lm/m^2 x 20 m^2 which again gives 1000 lumens.

    I hope that helps.

    Fizix