topic Why isn't IR image blurred? in Items with no label

Why isn't IR image blurred?

GPark7 — Wed, 23 Jan 2019 18:52:06 GMT

Hello.

I'm studying motion blur in TOF camera.

I'm using F200 of realsense.

The following images are IR and depth image while my hand is moving fast. As you see, the depth image is blurred .

However, why isn't the IR image blurred?

Thank you for your time.

Re: Why isn't IR image blurred?

MartyG — Wed, 23 Jan 2019 18:58:09 GMT

RealSense camera do not use Time of Flight (ToF) technology. An example of an ToF camera is the Kinect V2. So if the non-blurred IR image above was made by a RealSense camera such as the D415 or D435, it may not be helpful to your study of ToF technology, because a ToF image cannot be directly compared with the camera technology that RealSense uses.

RealSense F200 and SR300 are Structured Light / Coded Light

RealSense R200, ZR300, D415 and D435 are Stereo.

Kinect 1, meanwhile, was a Structured Light camera like the F200 / SR300.

Which camera are you using, please?

Re: Why isn't IR image blurred?

GPark7 — Wed, 23 Jan 2019 19:35:43 GMT

Thank you for your reply.

I'm using F200.

May I ask the reason why the IR image is not blurred?

Is this unique characteristic of structured light/ coded light camera?

If I use ToF camera (Kinect V2) or Stereo camera (R200, ZR300, D415 and D435), does it blur or not?

Thank you.

Re: Why isn't IR image blurred?

MartyG — Wed, 23 Jan 2019 19:58:17 GMT

I would expect the depth image to be blurred if you are moving your hand quickly in front of an F200. This is because it uses a slow Rolling Shutter that can cause artifacts such as streaks and blurs when observing fast motion. Camera models with a faster Global Shutter cope better with tracking motion. A data sheet document was never produced for the F200 so it is hard to get details of its exact specification. I believe its IR sensor used a faster Global Shutter though, which could account for a lack of motion blur on IR images. The link below backs this up:

https://software.intel.com/en-us/forums/realsense/topic/611014#comment-1862304

Re: Why isn't IR image blurred?

GPark7 — Wed, 23 Jan 2019 20:22:19 GMT

Thank you for your reply.

In my opinion, I think that the type of shutter doesn't affect phenomenon of the blur.

As you said, the faster speed of the shutter is, the less blur is.

In this context, I'm still curious of the reason why the IR image is not blurred.

Please, see the following link:

http://image-sensors-world.blogspot.com/2015/01/intel-releases-more-details-on-its-f200.html

As you see, the number of IR sensor is one.

The depth and IR image is made by the IR sensor.

So, the IR image and depth image are made with the same speed of the shutter.

How do you think of this?

Thank you for your time, again.

Re: Why isn't IR image blurred?

MartyG — Wed, 23 Jan 2019 20:30:15 GMT

I would recommend reading pages 13 and 14 of the SR300's data sheet for the explanations of how the structured light system calculates the depth and IR frames, since the F200 and SR300's tech is pretty similar.

https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/realsense-sr300-datasheet1-0.pdf

Re: Why isn't IR image blurred?

GPark7 — Thu, 24 Jan 2019 08:46:23 GMT

Thank you very much for the information!

I saw that there are increasing spatial frequency coded IR vertical bar patterns in depth video data flow.

On the other hand, the IR video data flow has a single pattern (a white I1).

It means that the IR video captures the scene for a shorter time than the depth video does when moving my hand quickly.

It is why the IR image is less blurred in my figure.

Do you think that this is correct?

Re: Why isn't IR image blurred?

MartyG — Thu, 24 Jan 2019 15:35:34 GMT

Your theory sounds reasonable, though I do not have knowledge of the hardware to that level of detail to confirm it *smiles* I would speculate that the shutter type (rolling on RGB versus global on IR) is the major factor in lack of IR image blur.

A company called Chipworks did a "teardown" analysis of the F200 hardware that you may find useful if you have not seen it already.

http://www.chipworks.com/about-chipworks/overview/blog/inside-the-intel-realsense-gesture-camera

Re: Why isn't IR image blurred?

GPark7 — Wed, 30 Jan 2019 15:14:32 GMT

Thank you very much for the information!

I'll test the blur with other devices as D435, D415, and Kinect1.