Which polarizer to buy for an OAK-D Pro W PoE camera

ZhifeiShen

Hi,

I want to add cross-polarization into my computer vision setup with the OAK camera and light sources. However, my lighting vendor is requesting more information about which type/specification of polarizer is most suited for the OAK camera, such as a size spec in mm. The polarizer also needs to be washdown-proof.

Many thanks in advance!

Zhifei

erik

Hi @ZhifeiShen ,
Current cameras don't have a an out-of-the-box solution, but some folks have glued a polarizing filter sheet to the front glass (just not at the lenses). Future devices (OAK4) will have a snap-on option for filters (ND, polarizing, etc). Thoughts?
Thanks, Erik

MariaPatni

erik

Hi @erik

I'd like to add a polarized lens to an OAK4 Camera, but I don't see any documentation for this and I'm not really sure where to start.

How do I decide the best one to to buy? Are there ones you recommend? What information do I need to know before choosing a lens?

Any help would be appreciated - thanks!

OskarSonc

Hey MariaPatni - Erik doesn't work at Luxonis anymore... So currently there is no official add-on lens for OAK4 yet. I will ask the team about this and will get back to you.

Thanks,
Oskar

OskarSonc

Hey @MariaPatni - for how many units would you need this? We think the easiest will be for you to buy polarizing glass straight from the amazon, test and then let us know which polarizer you would like to get on the final product/custom sku which we can then print out for you...

MariaPatni

Hi Oskar

We tested on Oak LDR Camera here

We bought a linear polarizing lens from Amazon (see here)
https://www.amazon.com/dp/B0C2PCFBCB?psc=1&ref_=cm_sw_r_cp_ud_ct_SFVHTWPC42AZR3YVA478

All I did was adhere the lens to the front of the camera as shown here:

However, the outputs when streaming don't look great.

The first 2 images are outputs with the polarized lens, the last one is without. You can see its noticeably better quality. I tried messing with the exposure, & toggling between Default Robotics and High_detail stereo presets with no improvements. Wondering if you have any intuition for how to improve this. Our use case is looking down at roads, which reflect lots of light messing with our depth maps.

OskarSonc

Hey MariaPatni - thanks for the test and photos. A linear polarizer will usually cut a lot of light (often50%+), so if stereo was already close to the “not enough texture/light” limit, depth and even the stream quality can look worse. Also I think the direction of filter blocked the screen light and that's one more reason why you got that results...

For roads/reflections it should still help, so I’d first sanity-check the setup: rotate the polarizer while looking at the reflection (a 90° rotation should noticeably change how much glare is suppressed), and make sure there isn’t a thin protective film still on the filter/foil. Also, could you share the raw left/right (rectified) stereo images used for the depth/pointcloud (and ideally a photo of how the filter is mounted)? It’s hard to diagnose from pointcloud alone, and the mono frames will show immediately whether this is light starvation, misalignment, or a mounting/film issue.

Thanks,
Oskar