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Re: Optical Pendulum

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Hi,

Francois LE COAT writes:
>>> Do you know something about the experiment of the "Optical Pendulum"?
>>>
>>>      <https://www.youtube.com/watch?v=cDJZVWEvhrc>
>>>
>>> A camera is suspended upon a cable, and an image is shot at the rest
>>> position. Then you push the pendulum, so that the camera oscillates,
>>> and new images are acquired when the pendulum moves.
>>>
>>> The goal is to evaluate the eight parameters that determine the
>>> position of the camera, from the rest position to the actual one.
>>> Because the pendulum oscillates, we obtain a pseudo-sinusoidal.
>>>
>>> The eight parameters are the perspective transform that happens
>>> from an image, to the others. That means translations <Tx,Ty,Tz>
>>> rotations <Rx,Ry,Rz> and two perspective parameters <Sx,Sy>.
>>>
>>> That's what we can see in the above video. Each images, and the
>>> corresponding perspective transform parameters, compared to rest.
>>
>> The goal is to measure a global movement, when it is observed by the
>> camera. There are devices that determine the position, such as the GPS
>> (Global Positioning System). We can measure the inclination with a
>> gyrometer, the acceleration with an accelerometer, the speed with an
>> odometer. The goal is to measure all this by the image, with a camera.
>>
>> Why?
>>
>> For example when we send robots to the planet Mars (Perseverance and
>> Ingenuity recently), and we want to pilot them with the means at our
>> disposal... On planet Earth there is a positioning system by GPS, which
>> works with a network of satellites. But on Mars it does not exist. To
>> navigate on Mars, we find our way with a camera. To do this, you have
>> to measure the movement of the camera. This is the goal of our
>> experiment. Measuring the movement of the camera... The robots that
>> move on Mars have navigation cameras. These are their eyes. It's as
>> efficient as a GPS.
> 
> I made a new video demonstration, with the optical pendulum experiment:
> 
>      <https://www.youtube.com/watch?v=PXbWNW7duCY>
> 
> We can see the image taken at the pendulum's rest. Then each of the
> images, when it oscillates. We see the perspective transformation
> between each image, to the rest, in image plane, i.e. in two dimensions.
> Then using the parameters obtained in 2D from the transformation, a
> virtual camera moves in 3D, using Persistence Of Vision software.
> It is an illustration of the use that we can have in 3D of the
> parameters: in translation <Tx,Ty,Tz>, in rotation <Rx,Ry,Rz> and
> in perspective <Sx,Sy>. It is a question of determining from the images,
> the movement in space of the camera. The movement in space between two
> images is completely described by eight parameters. POV-Ray is very well
> suited to represent the trajectory in 3D, because it is a free image
> synthesis software. Of course, all these computations are not yet done
> at the rate of video. It will probably be necessary to design a hardware
> acceleration, to obtain a smoother video...

A new video from the Optical Pendulum was realized which is a little
smoother, dissociating acquisitions from the parameters' computation...

     <https://www.youtube.com/watch?v=N2SQStXsz6U>

It may help to understand. A 50 images sequence is first acquired,
and then processed sequentially. You may better perceive the
camera-pendulum's oscillation.

Best regards,

-- 
Dr. François LE COAT
CNRS - Paris - France
<https://hebergement.universite-paris-saclay.fr/lecoat>

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Optical Pendulum Francois LE COAT <lecoat@atari.org> - 2021-10-24 19:15 +0200
  Re: Optical Pendulum Francois LE COAT <lecoat@atari.org> - 2021-11-15 19:30 +0100
    Re: Optical Pendulum Francois LE COAT <lecoat@atari.org> - 2022-04-12 16:06 +0200
      Re: Optical Pendulum Francois LE COAT <lecoat@atari.org> - 2022-05-03 13:45 +0200
        Re: Optical Pendulum Francois LE COAT <lecoat@atari.org> - 2022-05-06 12:45 +0200
          Re: Optical Pendulum Francois LE COAT <lecoat@atari.org> - 2023-03-21 15:30 +0100
            Re: Optical Pendulum Francois LE COAT <lecoat@atari.org> - 2023-11-21 11:00 +0100

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