[ CS231n ] Introduction to Convloutional Neural Networks for Visual Recognition
Visual data on internet
- really hard to understand
Youtube
- 3초 동안 15시간 분량의 비디오가 유튜브에 업로드됨
This lecture focuses on neural networks and CNN and visual applications
TOPIC
A brie history of computer vision
Evolution's Big Bang
- fossil studies : 10 million yeasr - the number of animal species 🔝
-around 540 million years : animals began to have eyes - they got VISION ❗️ =the biggest sensory system
History of Human's vision:
1600s : camera obscura
Hubel and Wiesel (1950~1960s)'s work
- used electrophysiology
- "what was the visual process mechanism like in mammals, primates...?"
- 고양이 뇌로 실험:
visual process starts with simple structure -> the brain builds up the pathway => understand complex visual world
Block World by Larry Roberts,1963
The Summer Vision Project, 1966
David Marr,1970s
Generalized Cylinder, Brooks & Binford, 1979 && Pictorial Structure, Fischler and Elschlager, 1973
Every object is composed of simple geomertric primitives
IF it is hard to recognizae object maybe we should first do object segmentation
HOW?
1. Take an image
2. Grop the pixels into meaningful areas //can't tell if the pixels were a person or a background
"AdaBoost Algorithm"
SIFT, David Lowe, 1999
- find critical features and match the features to a similar object
Spatial Pytamid Matching
The quality of image improved meanwhile
PASCAL Visual Object Challenge: 20 object recognition
=> Are we ready to recognized things in the real world?
=>AdaBoost: high possibility of overfit !
The Image Classification Challenge:
Result = Top 5 possible object list- if answer is in the list? CORRECT
2012: error rate dropped! Winning algorithm =CNN(Convolutional Neural Network)
2012 had a remarkable breakthrough in neural network but it was not invented in 2012.
There were foundational works: 1998 LeCun et al. 2012 Krizhevsky et al. //had architerctural similarities
Factors contirbuted to advancement:
1. Computation -GPU 2. Improved data
The goal of computer vision:
If people see a picture even for a very short amount time , they can tell or even make stories upon the image
People can not only sort the objects in the image, but they see and understand the situation.