Stereoscopic PIV


Erfan Hamdi
erfan.hamdi@gmail.com
99209041
Dr. Shafiei

Headlines

Introduction
Experiment
Mutliview Geometry

[cs231-course notes, 2021, Savaretse. N.]
Applications
  • 3D Scene Reconstruction
  • Autonomous Driving
  • Stereoscopic PIV
Planes of Interest 🛠
  • Object Plane
  • Camera Plane
  • Image Plane
[PIV practical guide, 2007, Raffel]
Camera Pin-hole Model
  • Apperture is a small hole
[cs231-course notes, 2021, Savaretse. N.]
Apperture
[cs231-course notes, 2021, Savaretse. N.]
Lens
[cs231-course notes, 2021, Savaretse. N.]
Camera Extrinsics

\[\begin{equation} \begin{bmatrix} R & T \\ 0 & 1 \\ \end{bmatrix} \end{equation}\]

Camera Intrinsics

\[\begin{equation} \begin{bmatrix} \alpha & -\alpha \cot \theta & c_x\\ 0 & \frac{\beta}{\sin \theta} & c_y\\ 0 & 0 & 1 \\ \end{bmatrix} \end{equation}\]

Stereoscopic PIV
ScheimpFlug Principle
[Scheimpflug Principle, Wikipedia Entry]
ScheimpFlug Principle
[Scheimpflug Principle, Wikipedia Entry]
ScheimpFlug Principle
[Scheimpflug Principle, Wikipedia Entry]
Experiment Setup

Translate

[PIV practical guide, 2007, Raffel]
Experiment Setup

Rotate

[PIV practical guide, 2007, Raffel]
Calibration
  • To reconstruct the local displacement vector
  • The Correspondence between the image and object space
[cs231-course notes, 2021, Savaretse. N.]
Calibration

\[\begin{aligned} X &= a_0 + a_1 x + a_2 y + a_3 x y + a_4 x^2 + a_5 y^2\\ Y &= b_0 + b_1 x + b_2 y + b_3 x y + b_4 x^2 + b_5 y^2\\ \end{aligned} \]

  • Solve using SVD
8 Point Algorithm
[cs231-course notes, 2021, Savaretse. N.]
Literature Review
Dual-Plane PIV
  1. Particle is in the Light sheet
  2. Particla moves out of plane
  3. Light sheet moves towards an out of plane direction
  • Raffel, Markus, et al. (1996).
[PIV practical guide, 2007, Raffel]
Holographic PIV
  • Light sheet is expanded into a thick slab.
  • Collier, Robert. Optical holography. Elsevier, 2013.
Experiment
[Stereoscopic PIV measurements using low‑cost action cameras, 2021, Kaufer]
Stereoscopic PIV measurements using low‑cost action cameras

Theo Kaufer
Experiments in Fluids
2021

Goal

Reduction of the cost of Stereoscopic PIV experiment.

Equipments
  • GoPro Hero 5
    • Sensor Size: 1.55um x 1.55um
    • 1280x720 @ 240fps
    • Rolling Shutter Mechanism
[GoPro.com]
Experiment
  • Thorlabs SOLIS-525C
    • 211Hz Pulse was Used
[Thorlabs.com]
Experiment
  • LaVision Calibration Plane GMBH-204-15
[LaVision.com]
Exp1: Planar PIV
  • Planar PIV using 1 Camera
  • Pulse and Continuous Wave Lighting
  • 128pxx128px interrogation window for first pass
  • 50% overlap
  • 24x24px interrogation for final pass
  • 75% overlap
Exp2: Stereoscopic PIV with plane tilt
  • Rotating disk can now tilt about z axis
  • Two cameras are in 30 degrees angle
  • Experiment setup
Exp3: Stereoscopic PIV on free jet
  • A pump is used to create the free jet right towards the camera plane
Dark ribbon phenomenon
  • Rolling Shutter Mechanism
[Rolling Shutter, Wikipedia Entry]
Dark ribbon phenomenon
  • Difference between light source pulse frequency and camera frame rate
Questions