Explanation of Aberration and Wavefront 1. What Causes Blur? 2. What is? 4. What is wavefront? 5. Hartmann-Shack Aberrometer 6. Adoption of wavefront technology David Oh
1. What Causes Blur? 2. What is? 4. What is wavefront? 5. Hartmann-Shack Aberrometer 6. Adoption of wavefront technology 2
1. What Causes Blur? Blurred vision is caused by light. Aberration simply means anything that prevents light from traveling in a straight line, i.e., something that causes the ray of light to be misdirected from its desired image point. Starbursts Halos and Ghost Images 3
1. What Causes Blur? 2. What is? 4. What is wavefront? 5. Hartmann-Shack Aberrometer 6. Adoption of wavefront technology 4
2. What is? Aberration simply means anything that prevents light from traveling in a straight line, i.e., something that causes the ray of light to be misdirected from its desired image point. 5
1. What Causes Blur? 2. What is? 4. What is wavefront? 5. Hartmann-Shack Aberrometer 6. Adoption of wavefront technology 6
3-1. Chromatic Chromatic Aberration Monochromatic The refractive index of crystalline lens vary with wavelength. Myopia Hyperopia Spherical Astigmatism Field curvature Coma Refractive index 1.415 1.410 1.405 1.400 Lens core 450 500 550 600 650 λ Distortion High order s Chromatic Aberration Refractive index variation 7
3-1. Chromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma The refractive index of crystalline lens vary with wavelength. Distortion High order s Chromatic Aberration After Compensation 8
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Myopia is a vision condition in which near objects are seen clearly, but distant objects do not come into proper focus. Myopia occurs if your eyeball is too long or the cornea has too much curvature, so the light entering your eye is not focused correctly. Distortion High order s Myopia 9
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma hyperopia is the inability to focus and see the close objects clearly, but in practice many young hyperopics can compensate the weakness of their focusing ability by excessive use of the accommodation functions of their eyes. Distortion High order s Hyperopia 10
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Spherical can be defined as the variation of focus with aperture. Distortion High order s Spherical Aberration 11
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Spherical can be defined as the variation of focus with aperture. Distortion High order s Spherical Aberration 12
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Astigmatism means that the cornea is oval like a football. Most astigmatic corneas have two curves a steeper curve and a flatter curve. This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near. Distortion High order s Astigmatism 13
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma That form of where points from an extended object make clear images at varying distances from the objective lens depending on the varying distances of the object points off the system axis. Distortion High order s Field Curvature 14
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength. Distortion High order s Coma Aberration 15
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Distortion High order s Coma Aberration After Compensation 16
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia An in an optical element which causes straight lines in the object, which are off the axis, to appear as curved lines in the image. Spherical Pincushion Astigmatism Field curvature Coma Distortion High order s Barrel Distortion 17
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Distortion First-order s include piston (plano) and prism (tilt). Second-order s include sphere (defocus, or more simply put, myopia and hyperopia) and cylinder. Everything higher than the second order is considered an HOA. High order s Zernike Modes 18
3-2. Monochromatic Chromatic Aberration Monochromatic Myopia Hyperopia Spherical Astigmatism Field curvature Coma Distortion High order s Myopia Hyperopia Spherical Astigmatism Field curvature Coma High order s 19
1. What Causes Blur? 2. What is? 4. What is wavefront? 5. Hartmann-Shack Aberrometer 6. Adoption of wavefront technology 20
4. What is Wavefront? Light rays travel in a wave like action from the source. If you were to connect the peaks(or valleys), what you would see is a series of concentric circles or flats that are called wavefronts. Peak Valley At a close distance to the source At a much longer distance to the source 21
4. What is Wavefront? 4-1. Wavefront of a convex lens parallel beam = plane wavefront converging beam = spherical wavefront 22
4. What is Wavefront? 4-1. Wavefront of a convex lens Defocused Wavefront Aberrated Wavefront Ideal Wavefront Defocused Wavefront Ideal Wavefront Aberrated Wavefront 23
4. What is Wavefront? 4-2. Wave Aberrated Beam Wave Aberration Ideal Wavefront Irregular Wavefront Wave Abberation 24
1. What Causes Blur? 2. What is? 4. What is wavefront? 5. Hartmann-Shack Aberrometer 6. Adoption of wavefront technology 25
5. Hartmann-Shack Aberrometer 5-1. Capturing wavefront exiting Incoming Wave LASER BEAM Lens System togenerate a point at the retina CCD-Image Outgoing Wave CCD camera captured wavefront exiting CCD-Camera Lens Array 26
5. Hartmann-Shack Aberrometer 5-2. Wavefront presentation process 27
5. Hartmann-Shack Aberrometer 5-2. Wavefront presentation process Calculating with wavefront exiting Local slopes Wavefront rebuilt Lenslet Array y(x 1, y 1 ) Aberrated Wavefront y(x 1, y 2 ) y(x 1, y 3 ) y(x 1, y 4 ) Focal Length f 28
5. Hartman-Shark Aberrometer 5-3. Wavefront and eye Ideal optical system Aberrated optical system CCD captured exiting CCD captured exiting An ideal optical system has a flat map. An aberrated eye has an undulating map. 29
5. Hartman-Shark Aberrometer 5-4. Zernike order Zernike order 5-5. Aberration and vision Aberration and vision 2 nd order 3 rd order 4 th order 30
1. What Causes Blur? 2. What is? 4. What is wavefront? 5. Hartmann-Shack Aberrometer 6. Adoption of wavefront technology 31
6. Adoption of wavefront technology 6-1. Optimized Contact lens Basic methods : Negative spherical balances the average positive spherical present in the eye EYE LENS EYE + LENS + = Z 400 Baseline = +0.15µm Contact lens (-1.00D) Eye + Contact lens = -0.02µm Z 400 32
Image Convolution Aberrometry Wave Aberration (PSF) Image Convolution Image Convolution Aberrometry Aberrometry Wave Aberration (PSF) Wave Aberration (PSF) 6. Adoption of wavefront technology 6-1. Optimized Contact lens Lower order correction (Myopia, Hyperopia, Astigmatism) Subject GY JP IC MM FE Subject GY JP IC MM FE Subject GY JP IC MM FE Higher order correction (Coma, Trefoil, etc) 33
6. Adoption of wavefront technology 6-2. Auto Ref-Keratometer HRK-7000 Acuity Map 34