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Original question:

DLP3000: Maximum incident power of monochromatic 450 nm laser

DLP3000: Maximum incident power of monochromatic 1040 nm laser

David Wilson12
Prodigy 120 points

Part Number: DLP3000

An experiment that uses DMD (DLP3000) with flash pumped Nd:YAG laser with an output power of 2.3mW and wavelenght of 1040nm resulted in a damaged DMD when all mirrors were set to the off-state.

Recommended operating conditions gives maximum illumination for wavelengths of greater than 700 nm is given as 10mW/cm^2. Clarity is required regarding these thresholds.

There are additional experiments planned but to avoid future damage it would be good to understand the root cause of the damage that has occurred in this case.

Note that the system was working fine before all the mirrors were set off so it is assumed that this is the root cause of the problem.

  • 0
    TI__Mastermind 23070 points
    Hi David,
    Thank you for your interest in DLP technology. Could you please share details about your experiment and application?
    DLP3000 DMD is recommended for visible wavelength (420 to 700nm) only. If your application requires 1040nm wavelength then please consider Near-infrared (NIR) products like DLP2010NIR and DLP4500NIR. These devices may be better suited for your application.
    www.ti.com/.../overview.html
    Regarding damage to DMD, there are several other factors which could impact power density ex. spot size of the laser, pulsing laser etc.

    Regards,
    Vivek
  • 0 in reply to Vivek Thakur
    Prodigy 70 points

    Dear Vivek Thakur

    A colleague and I from the Structured light Laboratory, University of the Witwatersrand, South Africa have been in contact with David, and the power generated by the laser is 2.3mW.

    According to Section 6.4 of DLP3000 DLP 0.3 WVGA Series 220 DMD datasheet (Rev. B) (please see the link), there is a stated Recommended operating illuminating condition of 10mW/cm^2 for wavelengths greater than 700 nm, which implies that the device should be able to operate at these wavelengths. As we are well below the illumination threshold, we do not understand how the device has sustained damage.  

    We would also like to understand:

    • If the thresholds is the same for all of the DMD states, for example if the threshold is the same in the sleep-mode(not connected to power) and in on-state (when mirrors are at angles of 12 degrees).
    • If this threshold is for the average or the peak power?
    • The filling factor in the sleep-mode is around 92%. What is the filling factor for the device in the on-state?
    • Transmission for the window on the micro-mirrors for wavelength 1.64 micrometers is around 78%, so the losses from this window is 22%. What is the percentage of light that got reflected and the percentage got absorbed by the window?
    • What is the power threshold for the silicon substrate under the micro-mirrors? 

    Thank you in advance.

    Sincerely,
    Ravin Kara

  • 0 in reply to Ravin Kara
    TI__Mastermind 23070 points
    Hi Ravin,
    Thank you for your patience. Please find response to your questions/observations:
    Ravin Wrote>
    --------------------------------------------------------------------------------------------
    According to Section 6.4 of DLP3000 DLP 0.3 WVGA Series 220 DMD datasheet (Rev. B) (please see the link), there is a stated Recommended operating illuminating condition of 10mW/cm^2 for wavelengths greater than 700 nm, which implies that the device should be able to operate at these wavelengths. As we are well below the illumination threshold, we do not understand how the device has sustained damage.
    -------------------------------------------------------------------------------------------------------------------
    Vivek> DLP3000 is designed for the visible light wavelength 420nm- 700nm. A typical wide spectrum light source also generates some amount of UV and NIR light. The MAX number if table 6.4 of the datasheet is referring to maximum exposure level for such wavelength when operating in the 420-700 wavelength range.
    It is likely that device might have damaged due to electrical issues like ESD, noise in the signal etc. You may also damage the device with laser if the laser beam is concentrated /point source, resulting in a very intensity at small location even though total power may be low or/and you pulse at a very high intensity for short duration.


    Ravin Wrote>
    --------------------------------------------------------------------------------------------
    We would also like to understand:
    • If the thresholds is the same for all of the DMD states, for example if the threshold is the same in the sleep-mode (not connected to power) and in on-state (when mirrors are at angles of 12 degrees).

    Vivek> The operation of the device is thermally limited; you need keep array temperature in the recommended operating range 40-70 C.

    • If this threshold is for the average or the peak power?
    Vivek> Typical use case is continues exposure i.e 100% duty cycle. These values are for continues exposure and it is recommend that peak values be similar or closer these level.

    • The filling factor in the sleep-mode is around 92%. What is the filling factor for the device in the on-state?
    Vivek> DLP3000 fill factor in on-state is ~94%+

    • Transmission for the window on the micro-mirrors for wavelength 1.64 micrometers is around 78%, so the losses from this window is 22%. What is the percentage of light that got reflected and the percentage got absorbed by the window?

    Vivek> Please refer to the following application note , the figure 1 of Page 2 , there is graph for windows transmissive response
    www.ti.com/.../dlpa031c.pdf

    Majority of the lost light is reflected, a very small component is absorbed.

    Even though window transmission response may seems acceptable 70% compared to 96%+ for visible light, the overall DMD efficiency will very low at 1040 nm for DLP3000 when you factor diffraction, internal reflection etc. In addition, image quality will be poor due to stray light from reflection from windows and also internal reflection. Please the DMD device design for NIR application like DLP2010NIR and DLP4500NIR if you need to operate at these wavelength.

    • What is the power threshold for the silicon substrate under the micro-mirrors?
    Vivek> There is no such specification.

    regards,
    Vivek
  • 0 in reply to Vivek Thakur
    Prodigy 70 points

    Dear Vivek Thakur

    Thank you for response, and my sincere apologies for the delayed reply.

    We are still unclear about the following:

    • There is a recommended operating condition which specifically states a maximum illumination threshold of 10mW/cm^2 for wavelengths greater than 700 nm (please see image below). I have made a red box of the stipulated recommended operating condition.

     

    • It is clearly stated that there is such a recommending operating condition. As we are well below this illumination threshold, even during short pulses, we are still not clear on how the device sustained damage. We are unsure of the type of electrical problems that may have caused damage, may you please be more specific on this matter?
    • Figure 1 page 2 of www.ti.com/.../dlpa031c.pdf refers to devices with Corning 7056 window transmission curves. The DLP3000 has the Corning XG window, which has transmittance of more than 80% for the visible and NIR coatings.

    Thank you for your assistance with regards to the other issues mentioned.

    Ravin Kara

  • 0 in reply to Ravin Kara
    TI__Mastermind 23070 points
    Hi Ravin,
    It is very likely damages may be due to some factors likely electrical, not optical.
    regards,
    Vivek