vision

Question 1

How to define the camera position

Answer 1

The camera position can be defined by a translation [Tx, Ty,Tz] and a rotation in the 3D space which is represented by 3*3 matrix

Question 2

How to define the reotation in the 3D space

Answer 2

it can be defined by 3 values, euler angles that can be represented by a 33 matrix, know that all the 3D rotations can be represented by a 33 matrix but not all the 3*3 matrices are 3D rotations

Question 3

what are the Euler angles

Answer 3

the describe 3angles that define the orientation of a rigid body

Question 4

what are the extrinsic parameters

Answer 4

correspond to the combination of the rotation and translation to define the camera

Question 5

what is the main idea behind a pinhole camera

Answer 5

project 3D points in the space to a 2D one, such that every 3D point is represented by 2 points of the sensor

Question 6

what is the difference between extrinsic and intrinsic parameters

Answer 6

extensive is more related to the camera position and intensity are more related to the project of the points in the space

Question 7

what is the focal length

Answer 7

it is the distance between the the lens and the sensor , we use it to represent the sensor points in term of space points

Question 8

how can we represent the world coordinates to pixel coordinates

Answer 8

one can use the mixture of intrinsic and extrinsic parameters

Question 9

explain the stereovision settings

Answer 9

The image is seen by two cameras, they are both on the same epipolar line, the distance between them is called the baseline and their optical view is parallel to each other

Question 10

why the angle of the eye change and is not parallel all the time

Answer 10

through constantly modifying the angles leads to obtain wider fields between the intersection of the cameras projection

Question 11

why we may need the stereovision

Answer 11

stereovision allows acquiring the geometry of the object

Question 12

what is the disparity

Answer 12

reflects the difference in the projection

Question 13

what is the relation between the distance and the dipary

Answer 13

The higher is the distance the higher is the disparity

Question 14

How the objects are detecion happen

Answer 14

the idea is that when both camera projections meet, that field is captured

Question 15

How the objects are detected happen

Answer 15

the idea is that when both camera projections meet, that field is captured

Question 16

what is the relation between the disparity and the baseline

Answer 16

the lower is the baseline the lower is the disparity, the higher is the baseline the lower is the coverage and the higher is the accuracy

Question 17

why camera with fixed angles

Answer 17

a camera with fixed angles is less complex to deal

Question 18

how to build a disparity map

Answer 18

we need to perform point matching

Question 19

why increasing the baseline means increasing the accuracy

Answer 19

This is a matter of scale

Question 20

How to perform point matching

Answer 20

The idea is that we have a window that is horizontally moving throughout the acquired images, then the matching happens in the case of the part corresponding to the lowest SSD

Question 21

how to deal with the noise during point matching

Answer 21

this might be due to the size of the window hence increasing the noise might be a solution however this also leads to lose some of the details

Question 22

how to deal with the noise during point matching

Answer 22

this might be due to the size of the window hence increasing the noise might be a solution however this also leads to losing some of the details

Question 23

what is epipolar plane

Answer 23

it is a plane that joins the points of the space in the front of the camera and the two points of projection, this plane makes an intersection with the projection planes and outputs the epipolar lines

Question 24

what is the epipolar line for parallel camera

Answer 24

it is horizontal

Question 25

what are the intrinsic parameters

Answer 25

The Camera constant (C): describes the distance between the image plane and the projection centre.
x-y scale difference m
focal length f,

initially, the points of the space are projected to the sensor and are represented in terms of the focal loss, however, we may need to take into consideration the fact that :

• camera’s pixels may not be squared hence, fx,fy
• the optical center is not always 0 (cx,cy)
• skewness: the camera sensor may have skew in the x,y

Question 26

why the higher is the baseline the higher is the accuracy

Answer 26

since a higher baselin we can capture more depth thus more accuracy

Question 27

what is the relation between epipolar line and depth

Answer 27

epipolar line allow us to measure the depth