E'p—_‘— ___» f_,,_
`
`—
`
`Smart
`
`Mini-Cameras
`
`
`
`
`
`Edited by
`
`Tigr-an V. Balstian
`
`CRC Press
`Taylor &Francis Group
`
`
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 1
`
`

`

`Smart
`ini-Cameras
`
`Edited by
`Tigran V. Galstian
`
`0 CRC Press
`
`Taylor & Francis Group
`Boca Raton London New York
`
`CRC Press is an imprint of the
`Taylor & Francis Group, an informa business
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 2
`
`

`

`CRC Press
`Taylor & Francis Group
`6000 Broken Sound Parkway NW, Suite 300
`Boca Raton, FL 33487-2742
`
`First issued in paperback 2020
`© 2014 by Taylor & Francis Group, LLC
`CRC Press is an imprint of Taylor & Francis Group, an Informa business
`No claim to original U.S. Government works
`
`Version Date: 20130722
`
`(pbk)
`ISBN 13: 978-0-367-57631-8
`(hbk)
`ISBN 13: 978-1-4665-1292-4
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`
`Library of Congress Cataloging-in-Publication
`
`Data
`
`/ editor, Tigran V. Galstian.
`
`Smart mini-cameras
`pages cm
`Includes bibliographical references and index.
`ISBN 978-1-4665-1292-4 (hardcover : alk. paper)
`control. 2. Miniature cameras--Design and
`1. Miniature cameras--Automatic
`I. Galstian, Tigran, editor of compilation.
`construction.
`
`TR260.5.S63 2014
`771.3'2--dc23
`
`Visit the Taylor & Francis Web site at
`http://www.taylorandfrancis.com
`and the CRC Press Web site at
`http://www.crcpress.com
`
`2013028853
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 3
`
`

`

`I]
`--!APTER 1
`
`ns Design and Advanced
`nction for Mobile Cameras
`
`P. Clark
`
`Introduction
`Key Optical Definitions
`Construction of MCMs
`1.3.1 Physical Construction
`1.3.2 Electrical Construction and Photographic Performance
`1.3.2.1 Pixel Size and Image Quality
`1.3.2.2
`IR Sensitivity
`1.3.3 Lens Design for MCMs
`1 .3.3.1 Aspheric Surfaces
`1.3.3.2 Optical Materials
`1.3.3.3 Physical Length
`1.3.3.4 Chief Ray Angle (CRA)
`1.3.3.5 Lens Design Process
`Basic Performance Aspects
`1 .4. 1
`Image Quality
`1.4.2
`Image Sharpness
`1 .4.2.1 Limiting Resolution
`1.4.2.2 MTF
`1 .4.3 Relative Illumination
`1.4.4 Dynamic Range
`1 .4.5 Distortion
`1 .4.6 Sampling and Aliasing
`1 .4.6.1 Aliasing in MCMs
`1.4.7 Stray Light
`1 .4.7. 1 Flare, Ghosts
`1 .4.7.2 Veiling Glare
`
`-
`
`2
`6
`10
`10
`11
`12
`13
`13
`14
`14
`15
`16
`18
`18
`18
`18
`21
`21
`24
`25
`25
`26
`28
`29
`30
`30
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 4
`
`

`

`2 ■ Smart Mini-Cameras
`
`1 .5 Focusing Issues in MCMs
`1.5.1 Simple Thin Lens
`1.5.2 Depth of Field and Depth of Focus
`1.5.3 Fixed-Focus MCMs
`1.5.4 Adjustable Focus MCMs
`1.5.5 AF Systems
`1.5.6 Mechanical Systems
`1.5.7 Electrically Variable Lenses
`1.5.7.1 Electrowetting Liquid Lenses
`1 .5.7.2 Deformable Lenses
`1.5.7.3 LC Lenses
`1.5-.7.4 Other Optical Focusing: Lateral Motion
`1.5.8 Alternative Approaches
`1.5.8.1 Software Focusing and Extended Depth of Field
`1.5.8.2 Light Field Photography
`1.5.8.3 Array Cameras
`1.6 Adapting Mobile Device Cameras to Special Applications
`1 .7 Advanced Capabilities of MCMs
`Image Stabilization Systems
`1 .7.1
`1 .7. 1 . 1 Optical Image Stabilization
`1 .7.1 .2 Software Image Stabilization
`1 .7. 2 Zoom
`1 .7.3 Stereo 3D Photography
`References
`
`31
`31
`32
`32
`33
`34
`35
`36
`37
`37
`38
`38
`38
`38
`39
`39
`41
`43
`43
`43
`44
`44
`45
`47
`
`l'lWlft'#ilt"lffll'ff....,
`
`n•
`
`:nw
`
`~~rm•tr:r:
`1.1 Introduction
`The history of photography has been marked by developments
`that have dramatically changed the relationship of the photogra(cid:173)
`pher to the technology:
`
`. ~-11· 1
`
`·r·~!iifT1
`
`1 ■
`
`Imaging capability: First there was only monochrome, then full
`color. First only still photography, then cinema and video.
`Light sensitivity has continuously improved. Most recently,
`digital imaging has been developed, giving the photographer
`powerful image-processing and editing capabilities.
`Immediacy: Until instant chemical photography became avail(cid:173)
`able in 1948, chemical photography required the photogra(cid:173)
`pher to wait for processing to see the image. In the 1990s,
`digital cameras with liquid crystal (LC) displays allowed
`review of images. Cameras. in mobile phones
`immediate
`allow immediate electronic distribution of images.
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 5
`
`

`

`2 ■ Smart Mini-Cameras
`
`1 .5 Focusing Issues in MCMs
`1.5.1 Simple Thin Lens
`1.5.2 Depth of Field and Depth of Focus
`1.5.3 Fixed-Focus MCMs
`1 .5.4 Adjustable Focus MCMs
`1 .5.5 AF Systems
`1 .5.6 Mechanical Systems
`1.5.7 Electrically Variable Lenses
`1.5.7.1 Electrowetting Liquid Lenses
`1.5.7.2 Deformable Lenses
`1.5.7.3 LC Lenses
`1.5.7.4 Other Optical Focusing: Lateral Motion
`1.5.8 Alternative Approaches
`1.5.8.1 Software Focusing and Extended Depth of Field
`1.5.8.2 Light Field Photography
`1.5.8.3 Array Cameras
`1.6 Adapting Mobile Device Cameras to Special Applications
`1 .7 Advanced Capabilities of MCMs
`Image Stabilization Systems
`1 .7. 1
`1 .7. 1 . 1 Optical Image Stabilization
`1 .7.1 .2 Software Image Stabilization
`1.7.2 Zoom
`1 .7.3 Stereo 3D Photography
`References
`
`31
`31
`32
`32
`33
`34
`35
`36
`37
`37
`38
`38
`38
`38
`39
`39
`41
`43
`43
`43
`44
`44
`45
`47
`
`ii ....
`
`11111Wlli1
`·
`
`· nnnrnnw W"
`
`·
`
`· 1w•mr
`1.1 Introduction
`The history of photography has been marked by developments
`that have dramatically changed the relationship of the photogra(cid:173)
`pher to the technology:
`
`.
`
`.... FM
`
`ii' ......... ., .. ..
`
`Imaging capability: First there was only monochrome, then full
`color. First only still photography, then cinema and video.
`Light sensitivity has continuously improved. Most recently,
`digital imaging has been developed, giving the photographer
`powerful image-processing and editing capabilities.
`Immediacy: Until instant chemical photography became avail(cid:173)
`able in 1948, chemical photography required the photogra(cid:173)
`pher to wait for processing to see the image. In the 1990s,
`digital cameras with liquid crystal (LC) displays allowed
`review' of images. Cameras _in mobile phones
`immediate
`allow immediate electronic distribution of images.
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 6
`
`

`

`Lens Design and Advanced Function for Mobile Cameras ■ 3
`
`Convenience: Early photographers used plates that needed to
`be prepared and developed near the camera, so when dry
`emulsions became available the darkroom did not have to
`be transported. Single-plate exposures with large cameras
`gave way to portable roll-film cameras that could make
`many images without being reloaded. Improvements to film
`and lenses shortened exposure time, allowing handheld
`photography of moving subjects and in low illumination.
`Electronics helped nonexperts, first with automatic expo(cid:173)
`sure control and later with autofocus (AF) systems.
`
`The size of consumer cameras became steadily smaller, from
`box cameras and folding roll-film cameras to 35 mm cameras,
`and then to even smaller consumer film formats such as Kodak's
`disc-camera system. Digital cameras continued the trend toward
`smaller size cameras, reducing the sensor size, and eliminating
`optical viewfinders and large strobe systems from most consumer
`cameras.
`The miniature digital cameras that we see in many mobile
`phones and other products are an important step in that evolu(cid:173)
`tion. They allow the consumer the ability to record images at any
`time, with a device that is always at hand. The miniature camera
`modules (MCMs) are so small that their impact on the device
`size and portability is acceptable to the consumer, thus causing a
`revolution in the acquisition of still and video images. As with any
`digital camera, the images are instantly seen and using a mobile
`phone and the Internet, they may be instantly shared with anyone.
`Furthermore, miniature digital cameras are being applied to a
`wide variety of applications in addition to conventional photog(cid:173)
`raphy. Increasingly, automobiles are being fitted with small cam(cid:173)
`eras for safety monitoring. Insurance companies employ cameras
`to monitor behavior, reducing accident rates and costs. Mobile(cid:173)
`phone cameras are being adapted for >technical applications, and
`even gigapixel "super cameras" are being assembled from large
`arrays of miniature camera sensors (Brady and Hagen 2009).
`Table 1.1a and 1.1b show the comparative data for various
`types of cameras, configured for general photography. Table 1.1b
`extends Table 1.1a to include photographic performance informa(cid:173)
`tion. This is not a complete survey of commercially available prod(cid:173)
`ucts. It is just a sample, intended to indicate trends and illustrate
`the changes due to camera scale.
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 7
`
`

`

`TABLE 1.1 Comparison of Camera Formats
`(a) Miniature Camera Modules, Digital Cameras, and Film Cameras•
`
`Inch-
`Format
`
`Horizontal Vertical Diagonal Area
`(mm2) Mega pixels
`(mm)
`(mm)
`(mm)
`
`Miniature Camera Modules
`1.74
`2.32
`1/6
`2.10
`2.80
`1/5
`2.70
`3.60
`1/4
`3.60
`4.80
`1/3
`
`Digitol Still Cameras
`6.08
`1/2.3
`6.40
`1/2
`7.44
`l/1.7
`13.20
`23.60
`36.00
`
`APS-C
`FULL
`
`Film Cameras
`Disc
`APS-H
`35 mm
`6x6 cm
`4 X 5 in.
`
`11.0
`30.2
`36.0
`60.0
`127.0
`
`4.56
`4.80
`5.58
`8.80
`15.80
`24.00
`
`8.0
`16.7
`24.0
`60.0
`101.6
`
`2.90
`3.50
`4.50
`6.00
`
`7.60
`8.00
`9.30
`15.86
`28.40
`43.27
`
`13.6
`34.5
`43.3
`84.9
`162.6
`
`4.04
`5.88
`9.72
`17.28
`
`27.72
`30.72
`41.52
`116.16
`372.88
`864.00
`
`88
`504
`864
`3600
`12903
`
`Minimum Maximum
`Pixel
`Pixel
`{mm)
`{mm)
`
`Linear
`Scale
`(35mm
`reij (%)
`
`Area
`Typical
`Scale
`{35mm Minimum
`f/number
`reij (%)
`1-:,
`;
`
`1.3-2
`2-3
`3-5
`5-8
`
`12-16.6
`16
`10-12
`14.2
`12.2-24.7
`18.1-24.7
`
`0.0014
`0.0014
`0.0014
`0.0014
`
`0.0015
`0.0014
`0.0019
`0.0029
`0.0039
`0.0059
`
`0.0017
`0.0017
`0.0017
`0.0017
`
`0.0022
`0.0014
`0.002
`0.0029
`0.0055
`0.0069
`
`7
`8
`10
`14
`
`18
`18
`21
`37
`66
`100
`
`31
`80
`100
`196
`376
`
`0.4
`0.7
`1.1
`1.9
`
`3.1
`3.4
`4.6
`13
`43
`100
`
`10
`64
`100
`385
`1413
`
`2
`2
`2.4
`2.8
`
`2.8
`2.4
`2
`2
`2
`1.4
`
`2
`2
`1.4
`2.8
`4.5
`
`,1:1,
`
`■
`
`(/)
`
`3 a
`::::.
`s'.:
`5·
`~
`3
`a
`"'
`
`(I)
`
`Entrance
`Pupil
`Diameter
`
`1.14
`1.37
`1.47
`l.68
`
`2.1
`2.6
`3.6
`6.2
`11. l
`24.3
`
`5.3
`13.5
`24.3
`23.8
`28.4
`
`EFL
`
`2.28
`2.75
`3.53
`4.71
`
`6.0
`6.3
`7.3
`12.5
`22.3
`34.0
`
`10.7
`27.l
`34.0
`66.6
`127.6
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 8
`
`

`

`Typical
`Minimum
`Inch-Format f/number
`
`Miniature Camera Modules
`2
`1/6
`1/5
`2
`1/4
`2.4
`1/3
`2.8
`
`EFL
`
`2.28
`2.75
`3.53
`4.71
`
`Digital Still Cameras
`1/2.3
`2.8
`1/2
`2.4
`1/1.7
`2
`2
`2
`1.4
`
`APS-C
`FULL
`
`6.0
`6.3
`7.3
`12.5
`22.3
`34.0
`
`·1
`
`Relative Total
`Diagonal
`Relative Central
`Light
`(Airy_Disc_ Diagonal
`Illumination (°!o)C Gathered (%)C Diameter)
`(2"pixel)
`
`Pixels
`(AD _Diameter)
`
`Closest
`Infinity Focus,
`Depth of Field
`(Diopters)d mm (Hyp/2)d
`
`111,
`
`49
`49
`34
`25
`
`25
`34
`49
`49
`49
`100
`
`0.2
`0.3
`0.4
`0.5
`
`0.8
`1.2
`2.4
`6.6
`21.1
`100.0
`
`1,080
`1,304
`1,397
`1,597
`
`2,023
`2,484
`3,465
`5,911
`10,581
`23,029
`
`1,036
`1,250
`1,607
`2,143
`
`2,533
`2,857
`2,447
`2,735
`3,641
`3,667
`
`2.05
`2.05
`2.46
`2.87
`
`2.68
`2.46
`1.51
`0.99
`0.74
`0.34
`
`2.16
`1.48
`1.23
`1.01
`
`0.798
`0.650
`0.465
`0.273
`0.152
`0.070
`
`462
`674
`813
`990
`
`1,254
`1,539
`2,149
`3,662
`6,558
`14,277
`
`2
`2
`1.4
`2.8
`
`49
`49
`100
`25
`
`Film Cameras
`Disc
`10.7
`5.0
`5,068
`APS-H
`27.1
`12,858
`28.6
`35 mm
`34.0
`100.0
`23,029
`6 x6 cm
`66.6
`104.2
`22,582
`4 x5 in.
`4.5
`127.6
`10
`144.5
`26,932
`° Compared at the same diagonal field of view: 65° full (34 mm EFL for 35 mm format).
`6 "Total light gathered" is an estimate of how much light energy is collected to record the image. "Resolving capability" assumes a diffraction-limited lens.
`c 35 mm = 1 00%.
`d DOF based on the worst case of: 1- 2 pixel blur, 2- l Airy Disc blur, 3- Diagonal/ 1500 blur.
`
`0.318
`0.125
`0.070
`0.071
`
`0.060
`
`3,142
`7,971
`14,277
`14,000
`16,697
`
`......
`Cl)
`:::,
`"'
`CJ
`Cl)
`"' co·
`:::,
`a
`:::,
`a..
`)>
`~
`:::,
`r,
`Cl) a..
`2"'
`:::,
`r,
`::!".
`0
`:::,
`o' .,
`~
`0
`0--
`~
`~
`3
`Cl) a
`"'
`■
`u,
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 9
`
`

`

`6 ■ Smart Mini-Cameras
`
`1.2 Key Optical Definitions
`In this section, we introduce some key optical definitions, which
`are important to understand the operation and performance trad(cid:173)
`eoffs of miniature cameras. These are an incomplete introduc(cid:173)
`tion to the optics of imaging systems. Introductory optics texts,
`such as Smith (2007), should be consulted for more complete
`information.
`Effective focal length (EFL): EFL is the separation of an equiva(cid:173)
`lent ideal thin lens from the image it makes of an infinitely distant
`object (see Figure 1.1). EFL and subject distance determine the
`location and size of an image with respect to an ideal thin lens.
`The EFL may be positive (converging lens), infinite (e.g., a flat
`window), or negative (diverging), but it may not be zero (see opti(cid:173)
`cal power).
`Optical power: The inverse of EFL, optical power is often
`expressed in diopters (inverse meters). It is useful to consider opti(cid:173)
`cal power because it easily handles the transition from positive
`to negative focal lengths. It is also a good way to describe the
`lenses sometimes used for focus correction (see
`supplementary
`Section 1.5.7).
`Field ef view (FOV): FOV is the extent of the captured image.
`The FOV may be described in object space or in image space. In
`image space, it is defined by the size of the sensor, either as x and
`y dimensions or as a diagonal dimension. In object space, it may
`be defined by the extent of the photographed object, but we often
`assume a distant object and measure it as an angle. One must
`be sure to understand if it is the "full" FOV or the "semi-FOV"
`in mobile
`(measured from the optical axis). FOVs of MCMs
`phones are currently 60°-75° full (corner to corner).
`
`Principal ray
`
`Image _ EFL* tan
`(field angle}
`height -
`
`FIGURE 1.1 The relationship between the EFL of a thin lens, the field angle, and the
`image height. Infinite object distance.
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 10
`
`

`

`Lens Design and Advanced Function for Mobile Cameras ■ 7
`
`Paraxial approximation: The paraxial approximation describes
`the behavior of a lens in the limit of small aperture size and FOV,
`greatly simplifying ray-tracing calculations. It tells us the ideal
`behavior of a lens system, ignoring geometric errors (aberrations).
`A real lens system that is designed and built to perform well is
`usefully characterized by its paraxial behavior.
`Paraxial thin lens approximation: Any lens, or combination of
`lenses with a finite focal length can be substituted paraxially by
`a single thin lens. In this section, we will show some examples of
`lens behavior using the thin lens approximation. Figure 1.2, for
`example, illustrates a compound lens made up of three paraxial
`thin elements.
`Optical axis: A lens system is usually rotationally symmetric
`about an optical axis. In most cameras, the optical axis is intended
`to intersect the sensor at its center point, and the sensor surface is
`normal to the optical axis.
`Object space and image space: We will use the term object space to
`refer to the world outside the camera before light enters the lens
`system, and image space to mean after the light exits the optical
`system (the last lens surface). So, the sensor is in image space and
`the photographed subject is in object space.
`Aperture stop: The aperture stop is the physical feature that
`limits the light passing through
`the lens, for the on-axis (cen(cid:173)
`tral) field point (see Figure 1.2). The aperture stop is usu(cid:173)
`ally circular. In many cameras (but not in MCMs)
`its size is
`adjustable.
`Entrance pupil and entrance pupil diameter (EPD) (see Figure
`1.2): The entrance pupil is the image of the aperture stop in object
`space. We can see the entrance pupil if we look into the front of
`the camera lens to see the aperture stop. If the aperture stop is
`in front of the camera lens, the entrance pupil is identical to the
`aperture stop, but the aperture stoP,_E<!n be inside or behind the
`camera lens, so the location and size of the entrance pupil are not
`the same as the (physical) aperture stop.
`Exit pupil (see Figure 1.2): Analogous to the entrance pupil,
`this is the image of the aperture stop in image space (in other
`words, as seen from the sensor).
`J7number (fno): Also known as the relative aperture. Defined
`paraxially, this is the ratio:
`
`EFL
`fno=--·
`FPn
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 11
`
`

`

`8 ■ Smart Mini-Cameras
`
`Aperture stop
`
`Entrance pupil
`
`Exit pupil
`
`FIGURE 1.2 A triplet lens with three thin lens elements, an infinite object, with con(cid:173)
`the EFL, aperture stop, and entrance and exit pupils.
`structions from rays illustrating
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 12
`
`

`

`Lens Design and Advanced Function for Mobile Cameras ■ 9
`
`1,
`
`fno = ( 2nsin <pr
`
`
`
`More precisely,
`
`where n is the refractive index in image space (usually air, n = 1.0)
`and <p is the angle of the real principal ray (see Figure 1.2). If
`n = l, f/0.5 is the mathematically
`lowest possible fno, which is
`unrealizable in a camera; f/1.0 is a practical lower limit for camera
`lenses.
`to fno- 2• Traditional
`An image's light intensity is proportional
`cameras have variable fno settings, often in factors of 2x exposure
`(f-stops): f/1.4, f/2.0, f/2.8, f/4, and so forth. Lower numerical
`fnos, then, provide more intensity in an image, and their Airy pat(cid:173)
`tern is smaller (see hereafter), but their depth of focus is reduced
`and their geometrical aberrations may be larger. MCMs almost
`always have a single fixed fno. Currently, MCM fnos are typically
`between f/2.0 and f/2.8.
`Rays: Lens design and analysis often model light energy propa(cid:173)
`gation as geometrical "rays." The ray optics or "geometrical optics"
`model ignores the wave nature oflight.
`Chief ray: For a given field point, this is the ray that passes
`through the center of the entrance pupil and aperture stop (see
`Figure 1.1). The paraxial chief ray approximately tells us the scale
`of the image on the sensor, and the difference between the "real"
`chief ray and the paraxial chief ray at the sensor is a measure of
`distortion (see Section 1.4.4). The difference between chief rays of
`different colors tells us the lateral chromatic aberration.
`Principal ray: This is the ray from the on-axis field point that
`passes through the edge of the entrance pupil and aperture stop
`(see Figure 1.1). Wherever the principal ray crosses the axis, there
`· -~
`is an image of the object.
`(PSF): This is the distribution of light
`Point spread junction
`intensity in the image of an ideal point source. It might be the
`optical PSF (the optical image alone) or the recorded image PSF
`(optical plus sensor, etc.) (see Section 1.4.2).
`Aberrations: These are geometric errors of the lens design or con(cid:173)
`struction. Real imaging systems do not behave exactly like the par(cid:173)
`axial ideal. If rays are traced exactly, we find that aberrations can
`keep them from forming perfect geometric images. Aberrations
`can be classified according
`to their functional dependencies.
`Aberrations may change with wavelength, and they often increase
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`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 13
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`10 ■ Smart Mini-Cameras
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`as the FOV and aperture increase. Most aberrations degrade image
`sharpness, but "distortion" aberrations cause errors of image size
`and shape without affecting sharpness. Defocus blur may be treated
`as a geometric aberration. The variation of defocus with wavelength
`is a form of "chromatic aberration." The correction of geometrical
`aberrations is the reason for much of the complexity oflens designs:
`multiple lens elements and aspheric surfaces are used to minimize
`ray errors in a lens design. Aberrations are also caused by lens fab(cid:173)
`rication errors, such as incorrect surface shapes and misaligned lens
`elements.
`
`1.3 Construction of MCMs
`
`1.3.1 Physical Construction
`Currently, the mechanical construction of the lens of most M CMs
`is an assembly of injection-molded polymer parts. The sensor on
`a flexible printed circuit board is attached to a polymer "holder,"
`which is equivalent to the body of a conventional camera. In a
`fixed-focus camera, that holder usually has a precisely threaded
`hole that receives the lens barrel. This thread is used for focus
`adjustment at assembly, then the barrel is fixed in the thread with
`an adhesive. The lens barrel contains the stack of lens elements
`and apertures, centered in the barrel by tight mechanical toler(cid:173)
`ances (<10 µm). The apertures in the barrel and the stack define
`the aperture stop of the system and block stray light paths. An
`infrared (IR)-cut filter (Section 1.3.2.2) may be mounted either
`in the lens barrel or in the holder.
`The complexity of the lens design can vary. A very simple way
`to describe a lens design is with the number of elements: 1G2P
`means one glass element plus two plastic. Flat parts such as filters
`and windows are not counted. Most MCM lens designs at this
`time are 3P, 4P or 5P.
`The prevention of contamination is an important consideration
`in the design and manufacture ofMCMs. Very small specks of dust
`can cause visible defects in images if they settle close to the sensor.
`An alternative method is "wafer-scale" construction. The wafer
`concept of construction of integrated circuits has been extended
`to the construction of lenses. A large array of replicated opti(cid:173)
`cal surfaces is constructed on each side of a wafer, then several
`wafers would be stacked together, perhaps even with a wafer of
`image sensors. Then, the entire assembly would be "diced" apart,
`
`APPLE V COREPHOTONICS
`IPR2020-00905
`Exhibit 2028
`Page 14
`
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