Long Range getting out of focus (as a function of ambient temperature)?

k323r

Hi Luxonis-community,

This is my first post, so please excuse a certain lack of credibility in this forum. First off, I am a fan of the hard- and software, and we use exclusively oak-d stereo cameras in our hardware (we build sensors for offshore wind farm installations). Recently, we switched over to using OAK-D Long Range for improved depth measurements and the option to have a fixed focus (e.g. less susceptibility to strong vibrations). However, we noticed a somewhat weird behavior: After having the cameras in operation, the images get blurry. This happens with long range cameras, where we calibrate depth ourselves (but kept the original lenses), where we replaced the lenses and even cameras that came with a reasonable focus where we didn't touch the lenses. The behavior seems to correlate with temperature, though. It seems, however, quite unreasonable, that expansion of the lenses causes the cameras to get out of focus, the temperature range that we are seeing is between 40 - 60 degrees. Any ideas? -Thanks

k323r

Here is an update on the behavior. We warmed the unit up to around 55 degrees Celsius after having recalibrated the focus during increasing temperature, the camera went out of focus. After having reached 55 degrees Celsius, we reached focus again by rotating the M12 lens. For us, this confirms a thermal expansion issue. @Luxonis: any ideas?

jakaskerl

k323r
Huh. Thanks for reporting this. Thermal expansion is expected to worsen the depth accuracy and precision, not the lens focus...

Let me run some tests in the office and I'll get back to you. Just to confirm, you get this issue on stock m12 lenses? Does it happen on all three cameras or only on one?

Thanks
Jaka

k323r

Hi Jaka,

Thanks for your reply, appreciate it!

This happens on multiple long-range cameras and both with stock M12 lenses and narrow FOV lenses. We had 6 long-range cameras in production and can confirm the behavior on all units (both on the field and during debugging tests). Happens on all lenses too. Please let me know if you'd like us to run any other type of test.

Is there a way to get more verbose info out of the long-range units, e.g. temperature of the AR0234 themselves? We're using the depthai python package.

Cheers!