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Scalping monochromatic light source.

Jennifer Lu
Prodigy 80 points
Other Parts Discussed in Thread: DLP4500NIR, DLPC350

I need to get a spatial light modulator to adjust light intensity in addition to "on" and "off " of a NIR light source (830 nm, 1W).  I think that I need to buy  DLP4500NIR MDM  and DLPC350 controller. I would like to know if the controller can be used to adjust the intensity of a monochromatic light source. Also since there is a built-in LED driver, is there a specific light source that we need to use?

Thanks,

  • 0
    TI__Guru 54320 points

    Hello Jennifer,

    Welcome to the DLP Advanced Light Control section of the TI-E2E community.

    I am not sure what your end goal is here.  If you need to adjust the actual intensity of the NIR source the DMD will accomplish this by "pulse width modulation" (PWM) which assumes that the sensing element has an integration period, such as a human eye or a camera, so that when averaged over the integration period you recieve a cumulative amount of light based on the modulation.  The source intensity during the period will be either on or off.

    The LED driver is not specific to a particular source, but the light source must be modulatable and if you plan to have the controller adjust the source current (or intensity) then it must understand PWM input for the source.  The controller has two signals for 3 LED channels, typically for Red, Green, & Blue.  The signals are Enable and PWM.  Enable turns the source on or off and PWM set the intensity or current relative to its maximum value.  So if you request 75% the PWM signal will have a 75% duty cycle pulse width that the reciever must interpret to adjust the illuminator accordingly.

    Note:  The source intensity is separate from the µ-mirror grayscale PWM.  The source adjusts the intensity incoming to all µ-mirrors, whereas the grayscale image information adjusts the integrated intensity of each pixel by PWM so that the eye or camera "sees" a grayscale image.

    I hope this helps.

    Fizix

  • 0 in reply to Fizix
    Prodigy 80 points

    Dear Fizix: Thanks. Good to know that PWM can be used to adjust light intensity. My  final goal is to create a grayscale NIR pattern on a substrate of 14 mm by 14 mm. We need to add a beam expander in between DMD and our substrate. I am assuming that  PWM units are a part of a DMD. Since there are 3 LED channels, I would assume that there are 3 PWMs that can be used to control light source independently, am I right? If I have 3 light sources, 680 nm, 830 nm and 970 nm, how do I  "couple"  these lights with each respective LED driver and PWM.   

    It seems to me that a PWM modulates light intensity and any light source is modulatable. May I know what kind light source is not? What is the role of LED driver? on and off? 

    Thanks.

  • 0 in reply to Jennifer Lu
    TI__Guru 54320 points

    Hello Jennifer,

    If you wish to create grayscale patterns, then you would use the DMD (& controller) to creat such a pattern.  To be clear, generally the controller typically determines the bitplanes (pixel information to create grayscale patterns).  And also the solid state illumination modulation to create the "shortest" bits.

    To combine multiple wavelengths you typically use dichroics, which are basically either high or low pass wavelength filters.

    Fizix

  • 0 in reply to Fizix
    Prodigy 80 points
    Hello Fizix:
    I am thinking about using one NIR LED since we need to generate monochromatic NIR grayscale pattern. Therefore one light source, instead of 3 as for the case of RGB , will be used. I have a 830 nm LED.
    - It is unclear to me about how our light source can be coupled into the LED driver on DMD so that the NIR light can be modulated by PWD/DMD. May I know the function of the LED driver in DMD?
    - Is PWD (assuming that PWD is a solid-state illumination modulator) programed by software that can be downloaded from a TI website ? if so, please provide me the web link.

    Jennifer
  • 0 in reply to Jennifer Lu
    TI__Guru 54320 points

    Hello Jennifer,

    You only need to connect one of the LED signal groups.  LED_Enable and LED_PWM.  The receiving electronics should be able to interpret the PWM and adust your LED driver from 0 to max current to match 0% PWM to 100% PWM.  Many LED drivers already have this input.  You will need to find an LED driver that is matched to your 830 nm LED.

    Fizix

  • 0 in reply to Fizix
    Prodigy 80 points

    Thanks.  Is the LED driver built into  the DMD or  is there a slot for a connection?

    - If it is built-in,  can you recommend a vendor that can provide a  NIR LED diode that is compatible with  the LED driver that is built into the DMD?

    -If not, can you recommend a vendor for both diode and controller?

    We were planning to order an LED diode/mount and controllers for current and temperature from Thorlab. We have optics to generate a collimated beam with the needed diameter.  Based on my understanding, I need to find a LED mount with 3 connections, 2 for current/intensity and temperature controls and the other for an LED driver.

    Can you send me a link with the  info about the LED driver?  Thanks a lot.

  • 0 in reply to Jennifer Lu
    Prodigy 80 points
    A PWM modulates the intensity of every pixel. Am I right? If there is a uniform NIR irradiating on the DMD with its overall intensity controlled by an external controller, can we use the LED as a light sensor only.

    I copied this sentence from the brochure "Red LED PWM signal used to control the LED current". It seems to me that the LED driver communicates with the PWM. I do not know how to "link" our light output after a series of optics to the LED drivers. If you can tell me the function of the LED driver (current controller only or both current control and sensing) , it will help to clear up my confusion.
  • 0 in reply to Jennifer Lu
    Prodigy 80 points

    A PWM modulates the intensity of every pixel. Am I right? If there is a uniform NIR irradiating on the DMD with its overall intensity controlled by an external controller, can we use the LED as a light sensor only.

    I copied this sentence from the brochure "Red LED PWM signal used to control the LED current". It seems to me that the LED driver communicates with the PWM. I do not know how to "link" our light output after a series of optics to the LED drivers. If you can tell me the function of the LED driver (current controller only or both current control and sensing) , it will help to clear up my confusion.