Image Formation Flashcards
Name some types of light sources
- Direct/ Indirect
- Point/ Area
- Natural/ Artifical
What type of light is used for thermal imaging
Infrared
What is aperture?
The hole in a camera where light is let through
What happens to the depth of field when aperture increases
It gets narrower
What is the F-Number?
focal length divided by aperture, it describes the depth of field.
What is the bayes filter in digital cameras
The Bayes filter is a sampling pattern for capturing color images. The pattern contains twice as many green detectors as blue or red.
How do we transform the Bayes pattern to digital images
The colors are interpolated using techniques like nearest neighbor, bilinear, cubic or nonlinear interpolation.
Name some representations for 3D rotations
- Rotation matrix (SO(3)), euler angles, axis/angle, quarternions
What does it mean that lines and points are dual objects in projective geometry?
They have the same representation
Do all projective lines have Euclidean counterparts?
No, lines on the form [0,0,z] do not have euclidian counterparts and are known as lines at infinity
How do we find the intersection of two projective lines?
The intersection x, can be calculated as: x = l1 x l2
Name two types of radial distortion
Pincushion and barrel distortion
What is the circle of confusion?
When a point source in the world illuminates more than one point in the image, the distortion is called circle of confusion
Name the different parameters of the cameras intrinsic model
fu, fv = focallength in u and v direction
cu, cv = Optical center coordinates
s = skew parameter, 0 in modern cameras.
Describe the pinhole camera model
The pinhole camera lets light through a point aperture (infinitesimal small opening), with a detector behind. This will theoretically result in all objects being in focus, but in practice, no light will pass through and no image is created.
Name some different color spaces
RGB, HSI, Lab
What is the perspective camera model
u = K*[r, t] * X
Describe the lens equation
1/a + 1/b = 1/f.
What is the difference of pose and the transform T?
The pose is a general description of one coordinate frame in another frame.
The transform T is a matrix representation of the pose.
Name two properties of lines in the projective plane
- All lines in the projective plane intersect. Parallel lines intersect at infinity. l1 and l2 intersect at x = l1 x l2
- The line going through x1 and x2 is given by: l = x1 x x2
Describe the extrinsic and the intrinsic part of the perspective camera model
intrinsic: K
extrinsic: [R, t]
What is a homography in the projective plane?
A homography is a non-singular(one-to-one) linear transformation, unique up to scale. For P2 it is represented by a 3x3 matrix with 8 degrees of freedom.
