Optical Pendulum

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Francois LE COAT

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Oct 24, 2021, 1:15:16 PM10/24/21
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Hi,

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.

Best regards,

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

Francois LE COAT

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Nov 15, 2021, 1:30:06 PM11/15/21
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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.
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