User avatar
HermannSW
Posts: 1319
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Very bright light (for high framerate videos) safety considerations

Sat Jun 09, 2018 1:39 pm

For very high framerate video recording (up to 1007fps with Raspberry v2 camera) bright (1000lm) light is not sufficient (due to 1ms time for complete frame limiting shutter time). I used 5000lm light and that was fine.

Recently I connected all three 5000lm LEDs to 50W power for one, was a bit brighter than just one, but not much. Two days ago I found and ordered a very cheap 100W power supply similar to the 50W one I already have (for <8$ inclusive shipping).

Looking into 5000lm by accident (even if only partially like in this photo) is really bad. Will be worse for 10000lm or 15000lm.
viewtopic.php?f=43&t=214816&p=1322397&s ... e#p1322287
Image


Today I looked for welding safety glassed in building market and bought 2 welding helmet relacement glasses for less than 5$ in total.
I had no idea on the safety norms and looked it up afterwards:
European Standards relating to safety eyewear
EN169, 170,171 & 172
These deal with the shade and filtering characteristics of the eye protection.
...
and the high intensity light produced during Welding processes.
...
1.2 to 16 = Welding Filters for spectacles & goggles to EN169. Please note that shades greater
than 7 require a face shield
Interesting, for shade 9 and 10 I have, a face shield is required, but I assume that is meant for arc welding.

I did a test taking 8MP image with raspistill, v2 camera sensor 20cm away from safety glasses (with M12 mounted lens).
There was not much difference for human eye between the two photos for me, so I did gimp histogram analysis showing that shade9 photo is brighter than shade10. Will take shade 10 safety glass from now on when looking into 5000lm (or 10000/15000lm) light. In both images you can see (thanks to safety glass) the 50×100lm LEDs making 5000lm in total:
Image


Shade 10:
Image


Shade 9:
Image


P.S:
Using replacement glass diagonally covers my eyes, looking into 5000lm led as here is no problem, even for longer time:
Image
⇨https://stamm-wilbrandt.de/en/Raspberry_camera.html

https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://gitlab.freedesktop.org/HermannSW/gst-template
https://github.com/Hermann-SW/fork-raspiraw
https://twitter.com/HermannSW

sanjaya
Posts: 14
Joined: Thu Jul 05, 2018 11:00 am

Re: Very bright light (for high framerate videos) safety considerations

Wed Jul 11, 2018 10:25 am

hi,
i've read your other threads so i reckon you "need" the bright light to minimize rolling shutter effect?
might i suggest going with strobe? we've proven it works in both modes for ov5647
- frex-pad --> frex pin/pad acting as input (from an external global shutter)
- frex-i2c --> frex pin/pad acting as output (to signal an external global shutter)

for the pad mode, you'll need to either buy an arducam (with 4 pins exposed) or hack your way around.
for the i2c mode, you can use any ov5647 camera with hacky implementation
personal suggestion: go with the pad mode.

Code: Select all

struct sensor_regs ov5647_setup_frex_pad[] = {
  { STROBE_FREX_MODE_SEL, 0x08 }, // 0x3B07
  { SC_CMMN_PAD_OEN2    , 0xE8 }, // 0x3002
  { DVP_VSYNC_MODE      , 0x02 }, // 0x4704
  { SC_CMMN_PAD_PK      , 0x00 }, // 0x3011 // [1] enable frex; 0 == enable!!!
  { TIMING_HSYNCST      , 0x08 }, // 0x3817 // i'm setting to max shutter duration; around 340µs
  { STROBE_FREX_CTRL0   , 0x0F }, // 0x3B06
};
struct sensor_regs ov5647_setup_frex_i2c[] = {
  { STROBE_FREX_MODE_SEL, 0x09 },
  { SC_CMMN_PAD_OEN2    , 0xF8 },
  { STROBE_FREX_EXP_H1  , 0x5D },
  { STROBE_FREX_EXP_L   , 0xB7 },
  { STROBE_FREX_CTRL0   , 0x0F },
};
struct sensor_regs ov5647_emit_frex_i2c[] = {
  { STROBE_FREX_EXP_REQ , 0x01 }, // 0x3B08
};
frex-pad
you can verify with raspi-raw (after minor modification - in you know where)
- connect a pwm circuit to the frex pin (set it up to pulse according to desired fps)
- connect the strobe pin to the led
- start the pwm
- run the (modified) raspiraw with above registers

frex-i2c (hack)
for this i modified another application (raspiraw by rafael Muñoz Salinas)
- connect gpio to the led (it should be connected to the strobe pin, but this is a hack)
- modify the code such that every grab request emits i2c command to 0x3B08 as well as turn the led on for a short duration
caveats: sometimes the i2c command fail.

oot:
with short strobe duration the light won't be nearly as intense, but still very annoying.
another suggestion: turn to black light / ir?
extra cost would be incurred because
- the lines would have to be coated with appropriate reflective material, but it should help with detection pipeline because otsu might be able to come back as probable solution.
- special kind of band-pass filter would also be required for the camera unit.
* granted, the angle of the led, target and camera would play a huge role on the amount of reflected light ...

User avatar
HermannSW
Posts: 1319
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Re: Very bright light (for high framerate videos) safety considerations

Mon Mar 04, 2019 1:02 am

sanjaya wrote:
Wed Jul 11, 2018 10:25 am

Code: Select all

...
struct sensor_regs ov5647_setup_frex_i2c[] = {
  { STROBE_FREX_MODE_SEL, 0x09 },
  { SC_CMMN_PAD_OEN2    , 0xF8 },
  { STROBE_FREX_EXP_H1  , 0x5D },
  { STROBE_FREX_EXP_L   , 0xB7 },
  { STROBE_FREX_CTRL0   , 0x0F },
};
struct sensor_regs ov5647_emit_frex_i2c[] = {
  { STROBE_FREX_EXP_REQ , 0x01 }, // 0x3B08
};
...

frex-i2c (hack)
for this i modified another application (raspiraw by rafael Muñoz Salinas)
- connect gpio to the led (it should be connected to the strobe pin, but this is a hack)
- modify the code such that every grab request emits i2c command to 0x3B08 as well as turn the led on for a short duration
caveats: sometimes the i2c command fail.
Were you successful with "sensor_regs ov5647_setup_frex_i2c" register settings and got a global reset frame?
If so, do you have complete runnable code somewhere or can attach here?
I tried that register set and was not able to trigger FREX frame capturing via sending "sensor_regs ov5647_emit_frex_i2c" to board:
https://www.raspberrypi.org/forums/view ... 2#p1436904
⇨https://stamm-wilbrandt.de/en/Raspberry_camera.html

https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://gitlab.freedesktop.org/HermannSW/gst-template
https://github.com/Hermann-SW/fork-raspiraw
https://twitter.com/HermannSW

Monomoon
Posts: 4
Joined: Fri Mar 01, 2019 6:13 pm

Re: Very bright light (for high framerate videos) safety considerations

Tue Mar 05, 2019 12:52 pm

HermannSW wrote:
Sat Jun 09, 2018 1:39 pm
Looking into 5000lm by accident (even if only partially like in this photo) is really bad. Will be worse for 10000lm or 15000lm.
I think the danger of the light source depends on the surface brightness. Two LEDs with 10000 Lumen instead of one LED with 5000 still have the same maximum surface brightness, thus resulting in the same illumination intensity (energy per aerea) on your retina. This is definately more uncomfortable, but I don't think it's a bigger health risk.

User avatar
HermannSW
Posts: 1319
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Re: Very bright light (for high framerate videos) safety considerations

Wed Mar 06, 2019 6:20 pm

The safety replacement glasses from building market covered the eyes only barely, this allowed for no head movement with 5000lm light on.
Today I found a 10$ welding shield for the replacement glasses in building market and bought it:
https://www.amazon.de/Güde-Schweißschut ... ref=sr_1_4

Much bigger, the complete head is covered, nearly from ear to ear. This allows to move the head without risk to directly look into 5000lm or more led. You can see the bright 5000lm led through safety glass without issues. Head is covered even if more distant to shield like when taking this photo (the bright light is from camera flash):
Image
⇨https://stamm-wilbrandt.de/en/Raspberry_camera.html

https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://gitlab.freedesktop.org/HermannSW/gst-template
https://github.com/Hermann-SW/fork-raspiraw
https://twitter.com/HermannSW

User avatar
HermannSW
Posts: 1319
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Re: Very bright light (for high framerate videos) safety considerations

Fri Mar 22, 2019 10:19 pm

I did receive 9.90$ aluminum heatsink with cooling fan for 200W today from aliexpress in 13 days with free shipping ‒ this time for the safety of the led:
https://www.aliexpress.com/item/Aluminu ... 54974.html

The heatsink 8cm×8cm perfectly fit into a 10x10 lego piece hole. One level below top I have 8x8 hole only, so that the fan sits on that level. Below that there are small corner towers of height 4. The construction allows the air that gets pushed vertically to escape though the big side holes. I did put a 10000lm led with Arctic MX-4 thermal compound on top of the heatsink, added cables from two 38V/1.5A led drivers (to match the 100W led requirement) and taped the connections. I powered the fan from my constant current supply with 12V. The device shows that the fan only draws 100mA. I taped the infrared thermal gun for handsfree operation and fixated it with the 4 arm-Realacc so that the laser point is directed into 10000lm led center:
Image


The temperature rose slowly, but constantly. After 15 minutes it reached 68°C, but I wanted to be sure and let the setup run continuously for 30 minutes. I used welding shield to not only safe my eyes, but also allow android camera to take a photo -- temperature is still at 68.0°C after half an hour, seems the heatsink+fan do a pretty good job at keeping 100W led at acceptable temperatures:
Image


Last, but not least, a photo of the 10000lm led through welding shield safety glass with focus on the led:
Image
⇨https://stamm-wilbrandt.de/en/Raspberry_camera.html

https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://gitlab.freedesktop.org/HermannSW/gst-template
https://github.com/Hermann-SW/fork-raspiraw
https://twitter.com/HermannSW

Return to “Camera board”