Bài giảng Nhập môn thị giác máy tính - Chapter 4: Light and color capture - Lê Thanh Hải
Chapter 4 – Light & Color
4-1
Chapter 4
Light and Color Capture
J ames Hays , Brown Univers ity
Department of Mechatronics
Chapter 4 – Light & Color
4-2
Contents
• Review of lighting
– Color, Reflection, and absorption
• What is a pixel? How is an image represented?
– Color spaces
Department of Mechatronics
Chapter 4 – Light & Color
4-3
A photon’s life choices
• Absorption
• Diffusion
• Reflection
• Transparency
• Refraction
• Fluorescence
• Subsurface scattering
• Phosphorescence
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-4
A photon’s life choices
• Absorption
• Diffus ion
light
source
• Reflection
• Trans parency
• Refraction
λ
• Fluores cence
• Subs urface s cattering
• Phos phores cence
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-5
A photon’s life choices
• Abs orption
• Diffuse Reflection
• Reflection
• Trans parency
• Refraction
light
source
λ
• Fluores cence
• Subs urface s cattering
• Phos phores cence
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-6
A photon’s life choices
• Abs orption
• Diffus ion
light
source
• Specular Reflection
• Trans parency
• Refraction
λ
• Fluores cence
• Subs urface s cattering
• Phos phores cence
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-7
A photon’s life choices
• Abs orption
light
source
• Diffus ion
• Reflection
• Transparency
• Refraction
λ
• Fluores cence
• Subs urface s cattering
• Phos phores cence
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-8
A photon’s life choices
• Abs orption
light
source
• Diffus ion
• Reflection
• Trans parency
• Refraction
λ
• Fluores cence
• Subs urface s cattering
• Phos phores cence
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-9
A photon’s life choices
• Abs orption
• Diffus ion
light source
• Reflection
• Trans parency
• Refraction
λ1
Fluorescent scorpion. Image courtesy of The Firefly Forest.
λ2
• Fluorescence
• Subs urface s cattering
• Phos phores cence
Fluorescence occurs when a substance absorbs
radiation of one wavelength, and immediately
emits radiation of a different wavelength.
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-10
A photon’s life choices
• Abs orption
light source
• Diffus ion
• Reflection
λ
• Trans parency
• Refraction
• Fluores cence
• Subsurface scattering
• Phos phores cence
• Interreflection
Department of Mechatronics
Chapter 4 – Light & Color
4-11
A photon’s life choices
• Abs orption
• Diffus ion
• Reflection
light source
t=1
• Trans parency
• Refraction
t=n
• Fluores cence
• Subs urface s cattering
• Phosphorescence
• Interreflection
Phosphorescence is a related type of photoluminescence
in which absorbed radiation is re-emitted more slowly, so
phosphorescent objects can still glow for periods up to
several hours after the source of incident radiation is
removed.
Department of Mechatronics
Chapter 4 – Light & Color
4-12
A photon’s life choices
• Abs orption
• Diffus ion
light source
• Reflection
λ
• Trans parency
• Refraction
• Fluores cence
• Subs urface
s cattering
• Phos phores cence
• Interreflection
(Specular Interreflection)
Department of Mechatronics
Chapter 4 – Light & Color
4-13
The Eye
• Your eyes work a lot like a camera. The lens of a camera
focuses light onto the film inside. The cornea and lens in the
front of the eye focus light onto the back, where light-
sensitive tissue called the retina is located. When the retina
receives an image, it sends a signal through the optic nerve
to the brain for the image to be developed.
Department of Mechatronics
Chapter 4 – Light & Color
4-14
The Eye
The human eye is a camera!
• Iris - colored annulus with radial muscles
• Pupil - the hole (aperture) whose size is controlled by
the iris
• What’s the “film”?
– photoreceptor cells (rods and cones) in the retina
Slide by Steve Seitz
Department of Mechatronics
Chapter 4 – Light & Color
4-15
The Retina
Cross-section of eye
Cross section of retina
Pigmented
epithelium
Ganglion axons
Ganglion cell layer
Bipolar cell layer
Receptor layer
Department of Mechatronics
Chapter 4 – Light & Color
4-16
What humans don’t have: tapetum lucidum
Department of Mechatronics
Chapter 4 – Light & Color
4-17
Two types of light-sensitive receptors
Cones
cone-shaped
less sensitive
operate in high light
color vision
Rods
rod-shaped highly
sensitive operate
at night gray-scale
vision
cone
rod
Department of Mechatronics
Chapter 4 – Light & Color
4-18
Rod / Cone sensitivity
The famous sock-matching problem…
Department of Mechatronics
Chapter 4 – Light & Color
4-19
Electromagnetic Spectrum
Human Luminance Sensitivity Function
Department of Mechatronics
Chapter 4 – Light & Color
4-20
Measuring spectra
Spectroradiometer: separate input light into its different
wavelengths, and measure the energy at each.
Department of Mechatronics
Tải về để xem bản đầy đủ
55 trang
25500
Free
Bạn đang xem 20 trang mẫu của tài liệu "Bài giảng Nhập môn thị giác máy tính - Chapter 4: Light and color capture - Lê Thanh Hải", để tải tài liệu gốc về máy hãy click vào nút Download ở trên
File đính kèm:
- bai_giang_nhap_mon_thi_giac_may_tinh_chapter_4_light_and_col.pdf
