Vision & Color Human Vision LGN: Lateral Geniculate Nucleus 2
Human Eye Cornea: 角膜, 角膜是細胞結構 surface 並不 smooth 靠眼淚滋潤 smooth Optical Disk (blind spot): 盲點 Axons of all ganglion cells pass thru the optical disc on the way to the brain. Has no photo-receptors. Aqueous: 水質, 角膜和水晶體之間 Lens: 水晶體 Retina: 視網膜 Fovea: 小凹 Pupil: 瞳孔 Iris: 虹膜 3 Accommodation Changes in the lens shape and position with accommodation. Focal length is adjusted by changing the lens curvature to focus the image on the retina.the distance between near point 和 far point is called accommodation range or amplitude of accommodation, which decreases approximately linearly with age. 4
Myopia and Hyperopia Myopia 近視 Hyperopia 遠視 5 近視與遠視的校正 (correction) 近視的校正 遠視的校正 6
散光 Astigmatism 7 老花 Presbyopia As we grow older, the lens becomes less elastic. It loses its ability to change shape. (Esp. seeing things that are close up) 8
LASIK Laser In-Situ Keratomileusis ( 在原位 ) 9 LASEK Laser Epithelial Keratomileusis ( 上皮 ) Better choice for poor LASIK candidates including people with less corneal tissue, fewer haze outcomes than LASIK, preserves more corneal tissue than LASIK, no complications of stromal flap as in LASIK, less risk of dry eye than LASIK. 10
Display? (LCD, PDP, OLED ) 11 Retina Retina: 網膜, 影像形成之處, 主要是由感光細胞組成 light sensitive cells:rods and cones 12
Rods and Cones Rods:high sensitivity / work at low light levels / highest density around fovea( 小凹 ) / sending signal to neural cells by gathering from about 100 rods, therefore very sensitive / poor resolution Cones :high resolution but lower sensitivy (>1 lux) / can tell different colors/ three typ light sensing cones with peak sensitivities at 420(S) 534(M) and 564(L) nm At night / no color due to low sensitivity of cones/ poor image shape due to low resolution of rods romantic?? 13 Rods and Cones The relative sensitivity of rods and cones as a function of wavelength. 14
Rods and Cones Spectral Response of Rods and S-, S, M-, M, L-ConesL 498(Rods) nm 420(S-Cones) 534(M-Cones) 564(L-Cones)nm Density of Rods and Cones Fovea: only M-M and L-Cones L no S-Cones S and Rods 15 Color Deficiency Color Deficiency 16
Color Deficiency Color Deficiency 17 CIE Color Matching Function CIE: Commission Internationale d'eclairage 18
配色函數 Color Matching Function (CMF) Negative? 19 CIE XYZ 色彩座標系統之建立 CMFs are non-negative negative over visible wavelengths. (i.e. any color is represented by 3 positive values). Equal amounts of the Primaries produce white. (i.e. X=Y=Z for stimulus of equal luminance at each wavelength). The y color matching function is defined to match the luminous- efficiency function of the human eye. 20
CIE x(λ), y(λ), z(λ) 21 Tristimulus values of color: XYZ 22
CIE Chromaticity Chart CIE Chromaticity Chart y x 23 Coordinate in the chromaticity diagram Intensity L e,λ (Green) X 350 400 450 500 550 600 650 700 750 800 Wave Length (nm) 780 X( λ) = L x( λ) dλ 380 780 380 780 380 e, λ Y( λ) = L y( λ) dλ e, λ Z( λ) = L z( λ) dλ e, λ X(λ), Y(λ), Z(λ) CIE 1931 X ( λ) x( λ) = X( λ) + Y( λ) + Z( λ) Y ( λ) y( λ) = X( λ) + Y( λ) + Z( λ) Z( λ) z( λ) = X( λ) + Y( λ) + Z( λ) 24
White light Reference Source Illuminant E 1.2 L e,λ 1 Intensity 0.8 0.6 0.4 0.2 X 0 350 400 450 500 550 600 650 700 750 800 850 Wavelength (nm) 0.9 0.8 515 520 525530 535 540 780 X( λ) = L x( λ) dλ 380 780 380 780 380 e, λ Y( λ) = L y( λ) dλ e, λ Z( λ) = L z( λ) dλ e, λ X ( λ) x( λ) = X( λ) + Y( λ) + Z( λ) Y ( λ) y( λ) = X( λ) + Y( λ) + Z( λ) Z( λ) z( λ) = X( λ) + Y( λ) + Z( λ) y 0.7 0.6 0.5 0.4 0.3 0.2 510 505 500 490 495 485 545 550 555 560 565 570 575 580 585 590 595 600 605 610 615 625 635 x( λ) = 0.333 y( λ) = 0.333 z( λ) = 0.333 480 0.1 475 470 465 460 0.0 455 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 25 0.8 x Color Gamut Boundary 1.2 1 Intensity 0.8 0.6 0.4 0.2 X 0 350 400 450 500 550 600 650 700 750 800 850 Wavelength (nm) 0.9 0.8 515 520 525530 535 540 780 X( λ) = L x( λ) dλ 380 780 380 780 380 e, λ Y( λ) = L y( λ) dλ e, λ Z( λ) = L z( λ) dλ e, λ X ( λ) x( λ) = X( λ) + Y( λ) + Z( λ) Y ( λ) y( λ) = X( λ) + Y( λ) + Z( λ) Z( λ) z( λ) = X( λ) + Y( λ) + Z( λ) y 0.7 0.6 0.5 0.4 0.3 0.2 510 505 500 490 495 485 545 550 555 560 565 570 575 580 585 590 595 600 605 610 615 625 635 480 0.1 475 470 465 460 0.0 455 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 26 0.8 x
色域 Color Gamut 27 Additive Color Mixing Linearity of color mixing Di-chromatic: color can be mixed along the line connecting the two points Tri-chromatic: color can be mixed within the triangle Color gamut ( 色域 ): the largest color gamut can be reached by using LED technology. 28
Color Mixing: any given color can be reproduced by mixing any combination of colors on the chromaticity chart. Color Mixing 29 Mixing Colored Light Color Addition Additive Primary Colors: Red Green Blue 30
Mixing Colored Pigments Color Subtraction Subtractive Primary Colors: Cyan Magenta Yellow Black (optional) 31 Mixing Color Why blue + yellow pigment yields green color? 32
Primary Colors White Red Green Blue Yellow Cyan Magenta 33 Complementary Colors Complementary Colors - any two colors that add together to produce white e.g. magenta + green = white 34
Hue, Saturation, and Brightness (saturation) http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html 35 http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html 36
Munsell system 37 Color Temperature 38