WO2014168586A1 - Lens array packages and image capturing devices incorporating the same - Google Patents

Lens array packages and image capturing devices incorporating the same Download PDF

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Publication number
WO2014168586A1
WO2014168586A1 PCT/SG2014/000159 SG2014000159W WO2014168586A1 WO 2014168586 A1 WO2014168586 A1 WO 2014168586A1 SG 2014000159 W SG2014000159 W SG 2014000159W WO 2014168586 A1 WO2014168586 A1 WO 2014168586A1
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WO
WIPO (PCT)
Prior art keywords
lens array
package
thermal expansion
polymer
polymer fibers
Prior art date
Application number
PCT/SG2014/000159
Other languages
French (fr)
Inventor
Markus Rossi
Hartmut Rudmann
Mario Cesana
Original Assignee
Heptagon Micro Optics Pte. Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Heptagon Micro Optics Pte. Ltd. filed Critical Heptagon Micro Optics Pte. Ltd.
Publication of WO2014168586A1 publication Critical patent/WO2014168586A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/0006—Arrays
    • G02B3/0037—Arrays characterized by the distribution or form of lenses
    • G02B3/0062—Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
    • G02B3/0068—Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between arranged in a single integral body or plate, e.g. laminates or hybrid structures with other optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
    • G02B7/021—Mountings, adjusting means, or light-tight connections, for optical elements for lenses for more than one lens
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
    • G02B7/028—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation

Definitions

  • This disclosure relates to image capturing device and, in particular, to lens array packages that can be incorporated into array cameras and other image capturing devices.
  • Some image capturing devices such as cameras use an array of multiple lenses. Such cameras can capture data from multiple viewpoints using an array of sub-cameras. The data from the sub-cameras then can be combined, for example, to generate a single high-quality image.
  • Processing of images in an array camera can include various steps such as rectification, image fusion, and up-scaling or interpolation. Precise calibration between the lenses and the sensor positions can be critical for some image processing algorithms. To obtain high-quality images using powerful interpolation techniques, the relative position between the sub-sensors and the lenses should remain substantially constant.
  • One potential situation that can cause changes in the relative position of the sub- sensors with respect to the lenses is thermal expansion of the lenses and/or sub-sensors in the lateral (i.e., x-y) directions.
  • the sensors may expand by as much as about 1 micron ( ⁇ ) at temperatures above 50 °C.
  • plastic lenses may expand by as much as 5 ⁇ , and in some cases, by as much as 25 ⁇ , at temperatures above 50 °C. This can be particularly problematic if the lens array is formed as a single integrated piece.
  • thermal expansion can make the image processing algorithms largely ineffective in certain temperature ranges, which reduces the usefulness of the camera.
  • This disclosure describes various features that can be provided to help reduce or alleviate the effects of thermal expansion/contraction of the lens array material.
  • Such features include stress release cuts in the surface(s) of the lens array, a frame having a low constant of thermal expansion (CTE) embedded within the lens array, or polymer fibers wrapped around the lens array or around the lens array housing.
  • CTE constant of thermal expansion
  • Each of these features can be used alone or in conjunction with one or more of the other features for reducing or alleviating the effects of the thermal expansion/contraction.
  • the lens array packages described here can, in some implementations, be less susceptible to problems caused by changes in temperature. Thus, more stable calibration between the lenses and the camera sub-sensors can be achieved in some cases. This, in turn, means that a camera or other image capturing device incorporating such a lens array package is more likely to be able to be used successfully over a wider range of temperatures.
  • one or more parts of a housing for the lens array can be composed of a material having a relatively low CTE.
  • the sidewalls of the lens array package and/or a baffle can be composed of a polymer material having a linear CTE of no more than 15 x 10 "6 /°C at 20 °C.
  • a substrate can be composed of a glass or ceramic material having a linear CTE of no more than 15 x 10 "6 /°C at 20 °C.
  • FIG. 1 illustrates an example of a cross-sectional side view of a lens array package.
  • FIG. 2 illustrates a top view of a lens array including stress release cuts.
  • FIG 2A illustrate a top view of another lens array including stress release cuts.
  • FIG. 3 illustrates a cross-sectional side view of a lens array including stress release cuts formed by injection molding.
  • FIG. 4A illustrates a cross-sectional side view of a lens array including an embedded frame.
  • FIG. 4B illustrates a cross-sectional top view of the lens array of FIG. 4A.
  • FIG. 5A illustrates a cross-sectional side view of another lens array including an embedded frame.
  • FIG. 5B illustrates a top view of the lens array of FIG. 5A.
  • FIGS. 6A through 6D illustrate examples of polymer fibers wrapped around a lens array.
  • FIGS. 7A through 7D illustrate examples of polymer fibers wrapped around another lens array.
  • FIG 8 illustrates an example of polymer fibers wrapped around a lens array package.
  • a lens array package 20 includes a lens array 22 within a housing.
  • the housing can include sidewalls 24, a substrate 26 and a baffle 28.
  • Lens array 22 can be attached, for example, to sidewalls 24.
  • Optoelectronic sensors e.g., CMOS or CCD sensors
  • the sensors can be arranged, for example, as a one-dimensional (IxN) or two-dimensional (MxN) arrangement of sub-cameras (e.g., 2x2, 3x3, 4x4, etc.).
  • Spacers 24 and baffle 28 can be composed, for example, of a material (e.g., polymer, glass or ceramic) having a low linear coefficient of thermal expansion (CTE). Although some polymers have a linear CTE of at least 20 x 10 "6 /°C at temperatures of 20 °C and higher, the CTE can be lowered by adding an appropriate carbon or ceramic Filler material to the polymer.
  • a material e.g., polymer, glass or ceramic
  • CTE linear coefficient of thermal expansion
  • Suitable ceramic fillers include aluminum (Al) oxides and zirconium (Zr) compounds. Such fillers, or others, can be added to the polymer-based material to achieve a linear CTE of no more than 15 x 10 '6 /°C at a temperature of 20 °C.
  • sidewalls 24 and/or baffle 28 preferably are composed of a material having a linear CTE of no more than 15 x 10 "6 /°C at a
  • sidewalls 24 and/or baffle 28 are composed of a non-transparent material so as to reduce the effects of stray light.
  • Substrate 26 can be composed, for example, of a transparent glass or ceramic material that preferably has a linear CTE of no more than 10 x 10 " 6/°C at a temperature of 20 °C.
  • suitable materials include glass (linear CTE of about 8.5 x 10 ' 6 /°C) or borosilicate (linear CTE of about 3.3 x 10 "6 /°C).
  • Other glass or ceramic materials that have a relatively low linear CTE can be used as well.
  • substrate 26 is structured to provide focal length adjustments for the individual lenses in lens array 22 so as to correct for variations in the focal lengths of the lenses. Further details of such a substrate structure are described in U.S. Provisional Patent Application No. 61/772,073.
  • Lens array 22 includes multiple lenses that can be arranged, for example, as a two-dimensional rectangular or linear array of lenses 30 and can be formed as a single integral piece.
  • lens array 24 includes lenses 30 on its top and bottom surfaces.
  • the lenses 30 can have an arrangement other than a rectangular or linear array.
  • the lenses 30 in array 22 may be arranged in a triangular or other ordered arrangement.
  • the lenses 30 can have the same size as one another or may have different sizes from one another.
  • Lens array 22 can be composed, for example, of a plastic material and can be formed, for example, by injection molding.
  • injection molded lens array 22 facilitates manufacturing and can be relatively inexpensive.
  • one potential issue is thermal expansion or contraction of the plastic material, which may have a linear CTE of 20 x 10 " 6 /°C or higher at a temperature of 20 °C.
  • various features, individually or in combination, can be provided to reduce or alleviate the effects of any such thermal expansion.
  • stress release cuts 32 can be provided in the top and/or bottom surfaces of lens array 22. Such stress release cuts 32 can help counteract thermal expansion of the injection molded plastic material of the lens array 22. In the illustrated example, stress release cuts 32 form a pattern in which some of the stress release cuts are substantially at a ninety-degree angle with respect to the other stress release cuts. Stress release cuts 32 can be formed alongside lenses 30 such that each lens (other than lenses along the periphery of the lens array) is surrounded by four stress release cuts 32. In the illustrated example, stress release cuts 32 are offset at an angle (i.e., a non-90° angle (a) such as a ⁇ 85°) with respect to the sides 34 of lens array 22.
  • a non-90° angle a
  • a cross-like arrangement of stress release cuts 32 can, in some cases, convert linear compression/expansion that would otherwise occur due to thermal changes into rotational movement so as to limit movement of the lens array in the lateral (x-y) directions.
  • a different number of stress release cuts can be provided, and the angle of the stress release cuts can differ from the illustrated examples of FIGS. 2 and 2A.
  • stress release cuts 32 can be provided in both the upper surface (baffle side) and lower surface (substrate side) of lens array 22. In some implementations, stress release cuts 32 may be provided in only one of the surfaces. Stress release cuts 32 can be formed, for example, by micromachining or etching the injected molded lens array 22. Alternatively, stress release cuts 32 can be formed as part of the injection molding process. For example, as indicated in FIG. 3, molds 40 for the injection molding process can include cut-out areas 42 that correspond to the areas for lenses 30, as well as projections 44 that correspond to the areas for the stress release cuts 32.
  • stress release cuts 32 can vary depending on the particular implementation. In some implementations, stress release cuts 32 extend only partially through the thickness of lens array 22 so as not to impact the structural stability of the lens array negatively. However, in some implementations, such as small arrays, stress release cuts 32 may extend through the entire thickness of the lens array (i.e., from the baffle-side surface to the substrate-side surface).
  • FIGS. 4A and 4B illustrate an implementation in which a frame 50 in the shape of a two-dimensional grid and having a low CTE is embedded within lens array 22.
  • a portion of frame 50 is disposed around lenses 30 near the periphery of lens array 22 and other portions of the frame are disposed in regions that separate adjacent lenses 30 from one another.
  • frame 50 is completely surrounded by the injection molded plastic material that forms lenses 30.
  • the plastic injection molded material covers the top and bottom surfaces of frame 50.
  • Frame 50 can be composed, for example, of a carbon-filled plastic material, a ceramic material or a glass material.
  • frame 50 should have a linear CTE less than the linear CTE of the plastic material of lens array 22.
  • the same polymer materials described above in connection with sidewalls 24 and baffle 28 can be used for frame 50.
  • the same glass and ceramic materials described above in connection with substrate 26 can be used for frame 50.
  • the embedded frame 50 can have a significantly lower CTE, which can help reduce the extent of any thermal expansion and contraction as the temperature changes.
  • FIGS. 5A and 5B illustrate another implementation of a lens array 22 with an embedded frame 50A of a low CTE material. As in the implementation of FIGS. 4A and 4B, a portion of frame 50A is disposed around lenses 30 near the periphery of lens array 22 and other portions of frame 50A separate adjacent lenses 30 from one another.
  • the injection molded plastic material of the lens array 22 does not cover the embedded frame 50A at its upper (baffle-side) surface and its lower (substrate- side) surface.
  • frame 50A (or 50) is composed of a non-transparent material, which can help reduce the effects of stray light.
  • polymer fibers having a low CTE can be wrapped around lens array 22.
  • polymer fibers 60 are wrapped around the outer surface of lens array 22.
  • polymer fibers 60 are wrapped over the upper and lower surfaces of lens array 22.
  • polymer fibers are wrapped around the side surfaces of lens array 22.
  • polymer fibers 60 are wrapped over the upper and lower surfaces of lens array 22 and also are wrapped around the side surfaces of lens array 22.
  • Polymer fibers 60 preferably have a relatively low CTE.
  • polymer fibers 60 should have a linear CTE less than the linear CTE of the plastic material of lens array 22.
  • polymer fibers 60 have a linear CTE no greater than 5.
  • polymer fibers 60 can be composed of an aramid type fiber having a CTE of about -2 x 10 "6 /°C at a temperature of 20 °C.
  • polymer fibers 60 are composed of a liquid crystal polymer fiber (e.g., VECTRAN ® material) having a CTE of ⁇ 4 x 10 "6 /°C at a temperature of 20 °C.
  • Other polymer fibers can be used as well.
  • FIGS. 6A through 6D illustrate wrapping polymer fibers 60 around a small lens array (i.e., a 2 x 2 array)
  • polymer fibers 60 can be wrapped around larger lens arrays as well (see, e.g., FIGS. 7A, 7B, 7C and 7D). Wrapping low CTE polymer fibers 60 around lens array 22 can help confine any lateral expansion of the lens array that may otherwise occur as a result of temperature changes. More generally, such polymer fibers 60 can be wrapped around the entire lens array 22, around portions of the array or around individual lenses 30. In such cases, polymer fibers 60 can be in direct contact with the surface(s) of lens array 22.
  • polymer fibers 60 can be wrapped around the outside of sidewalls 24 that form the housing of lens array package 20.
  • polymer fibers 60 having a low CTE are wrapped around, and are in direct contact with, the exterior surface of sidewalls 24.
  • the same types of polymer fibers described above in connection with FIGS. 6A-6D can be used for the polymer fibers 60 of FIG. 8.
  • one or more features can be provided to reduce or alleviate the effects of thermal expansion/contraction of the injection molded plastic lens array material.
  • Such features include stress release cuts in the surface(s) of the lens array, a frame having a low CTE embedded within the lens array, polymer fibers wrapped around the lens array or around the lens array housing, or a housing having sidewalls, a substrate and/or a baffle made of a low-CTE material.
  • Each of these features can be used alone or in conjunction with one or more of the other features for reducing or alleviating the effects of the thermal expansion/contraction.
  • the lens array packages described above can provide a lens array package that is less susceptible to problems caused by changes in temperature.
  • the array can take the form of a IxN array, an NxM (linear or rectangular) array, a triangular array or an array with some other arrangement.
  • Such arrays may be applicable, for example, to various ones of the embodiments described above (e.g., FIGS. 1, 2, 4A, 4B, 5A, 5B, 6C, 7C and 8).

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Abstract

Various features can be provided to help reduce or alleviate the effects of thermal expansion/contraction of a lens array material. Such features include stress release cuts in the surface(s) of the lens array, a frame having a low constant of thermal expansion (CTE) embedded within the lens array, or polymer fibers wrapped around the lens array or around the lens array housing. The features can be used alone or in conjunction with one or more of the other features for reducing or alleviating the effects of the thermal expansion/contraction. In addition, one or more parts of a housing for the lens array can be composed of a material having a relatively low CTE. The lens array package can be incorporated into a camera or other image capturing device.

Description

LENS ARRAY PACKAGES AND IMAGE CAPTURING DEVICES
INCORPORATING THE SAME
FIELD OF THE DISCLOSURE
[0001] This disclosure relates to image capturing device and, in particular, to lens array packages that can be incorporated into array cameras and other image capturing devices.
BACKGROUND
[0002] Some image capturing devices such as cameras use an array of multiple lenses. Such cameras can capture data from multiple viewpoints using an array of sub-cameras. The data from the sub-cameras then can be combined, for example, to generate a single high-quality image.
[0003] Processing of images in an array camera can include various steps such as rectification, image fusion, and up-scaling or interpolation. Precise calibration between the lenses and the sensor positions can be critical for some image processing algorithms. To obtain high-quality images using powerful interpolation techniques, the relative position between the sub-sensors and the lenses should remain substantially constant.
[0004] One potential situation that can cause changes in the relative position of the sub- sensors with respect to the lenses is thermal expansion of the lenses and/or sub-sensors in the lateral (i.e., x-y) directions. For example, in some array cameras, the sensors may expand by as much as about 1 micron (μηι) at temperatures above 50 °C. Likewise, in some array cameras, plastic lenses may expand by as much as 5 μηι, and in some cases, by as much as 25 μιη, at temperatures above 50 °C. This can be particularly problematic if the lens array is formed as a single integrated piece. Such thermal expansion can make the image processing algorithms largely ineffective in certain temperature ranges, which reduces the usefulness of the camera. SUMMARY
[0005] This disclosure describes various features that can be provided to help reduce or alleviate the effects of thermal expansion/contraction of the lens array material. Such features include stress release cuts in the surface(s) of the lens array, a frame having a low constant of thermal expansion (CTE) embedded within the lens array, or polymer fibers wrapped around the lens array or around the lens array housing. Each of these features can be used alone or in conjunction with one or more of the other features for reducing or alleviating the effects of the thermal expansion/contraction. The lens array packages described here can, in some implementations, be less susceptible to problems caused by changes in temperature. Thus, more stable calibration between the lenses and the camera sub-sensors can be achieved in some cases. This, in turn, means that a camera or other image capturing device incorporating such a lens array package is more likely to be able to be used successfully over a wider range of temperatures.
[0006] In some implementations, one or more parts of a housing for the lens array can be composed of a material having a relatively low CTE. For example, the sidewalls of the lens array package and/or a baffle can be composed of a polymer material having a linear CTE of no more than 15 x 10"6/°C at 20 °C. Likewise, a substrate can be composed of a glass or ceramic material having a linear CTE of no more than 15 x 10"6/°C at 20 °C. These features can be used alone or in combination with stress release cuts in the surface(s) of the lens array, a frame having a low CTE embedded within the lens array, or/and polymer fibers wrapped around the lens array or around the lens array housing. In The array can be, for example, a lxN array, an NxM (linear or rectangular) array, a triangular array or an array with some other arrangement.
[0007] Specific examples of the foregoing features, as well as other features, are described in greater detail. Other aspects, features and advantages will be readily apparent from the following detailed description, the accompanying drawings and the claims. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates an example of a cross-sectional side view of a lens array package.
[0009] FIG. 2 illustrates a top view of a lens array including stress release cuts.
[0010] FIG 2A illustrate a top view of another lens array including stress release cuts.
[0011] FIG. 3 illustrates a cross-sectional side view of a lens array including stress release cuts formed by injection molding.
[0012] FIG. 4A illustrates a cross-sectional side view of a lens array including an embedded frame.
[0013] FIG. 4B illustrates a cross-sectional top view of the lens array of FIG. 4A.
[0014] FIG. 5A illustrates a cross-sectional side view of another lens array including an embedded frame.
[0015] FIG. 5B illustrates a top view of the lens array of FIG. 5A.
[0016] FIGS. 6A through 6D illustrate examples of polymer fibers wrapped around a lens array.
[0017] FIGS. 7A through 7D illustrate examples of polymer fibers wrapped around another lens array.
[0018] FIG 8 illustrates an example of polymer fibers wrapped around a lens array package.
DETAILED DESCRIPTION
[0019] As shown in FIG. 1, a lens array package 20 includes a lens array 22 within a housing. The housing can include sidewalls 24, a substrate 26 and a baffle 28. Lens array 22 can be attached, for example, to sidewalls 24. Optoelectronic sensors (e.g., CMOS or CCD sensors) can be provided below substrate 26 to detect light entering lens array package 20. The sensors can be arranged, for example, as a one-dimensional (IxN) or two-dimensional (MxN) arrangement of sub-cameras (e.g., 2x2, 3x3, 4x4, etc.). Data from the sub-cameras then can be combined, for example, by a processing unit, which can include hardware and/or software, to generate a single high-quality image. The lens array package and sub-cameras can be incorporated into an image capturing device such as an array camera. [0020] Sidewalls 24 and baffle 28 can be composed, for example, of a material (e.g., polymer, glass or ceramic) having a low linear coefficient of thermal expansion (CTE). Although some polymers have a linear CTE of at least 20 x 10"6/°C at temperatures of 20 °C and higher, the CTE can be lowered by adding an appropriate carbon or ceramic Filler material to the polymer. Examples of suitable ceramic fillers include aluminum (Al) oxides and zirconium (Zr) compounds. Such fillers, or others, can be added to the polymer-based material to achieve a linear CTE of no more than 15 x 10'6/°C at a temperature of 20 °C. Thus, in general, sidewalls 24 and/or baffle 28 preferably are composed of a material having a linear CTE of no more than 15 x 10"6/°C at a
temperature of 20 °C. For example, carbon reinforced polycarbonate, with a linear CTE of 14 x 10"6/°C at a temperature of 20 °C, can be used for sidewalls 24 and/or baffle 28. As another example, a composite material of a polymer and Zr compound, with a linear CTE of ±3 x 10"6/°C at a temperature of 20 °C, can be used for sidewalls 24 and/or baffle 28. Preferably, sidewalls 24 and baffle 28 are composed of a non-transparent material so as to reduce the effects of stray light.
[0021] Substrate 26 can be composed, for example, of a transparent glass or ceramic material that preferably has a linear CTE of no more than 10 x 10"6/°C at a temperature of 20 °C. Examples of suitable materials include glass (linear CTE of about 8.5 x 10' 6/°C) or borosilicate (linear CTE of about 3.3 x 10"6/°C). Other glass or ceramic materials that have a relatively low linear CTE can be used as well. In some implementations, substrate 26 is structured to provide focal length adjustments for the individual lenses in lens array 22 so as to correct for variations in the focal lengths of the lenses. Further details of such a substrate structure are described in U.S. Provisional Patent Application No. 61/772,073.
[0022] Lens array 22 includes multiple lenses that can be arranged, for example, as a two-dimensional rectangular or linear array of lenses 30 and can be formed as a single integral piece. In the illustrated example of FIG. 2, lens array 24 includes lenses 30 on its top and bottom surfaces. In some implementations, the lenses 30 can have an arrangement other than a rectangular or linear array. For example, as shown in the example of FIG. 2A, the lenses 30 in array 22 may be arranged in a triangular or other ordered arrangement. Further, in some cases, the lenses 30 can have the same size as one another or may have different sizes from one another. Lens array 22 can be composed, for example, of a plastic material and can be formed, for example, by injection molding. Using a plastic, injection molded lens array 22 facilitates manufacturing and can be relatively inexpensive. However, as noted above, one potential issue is thermal expansion or contraction of the plastic material, which may have a linear CTE of 20 x 10" 6/°C or higher at a temperature of 20 °C. Nevertheless, as described in greater detail below, various features, individually or in combination, can be provided to reduce or alleviate the effects of any such thermal expansion.
[0023] As illustrated in FIGS. 2 and 2A, stress release cuts 32 can be provided in the top and/or bottom surfaces of lens array 22. Such stress release cuts 32 can help counteract thermal expansion of the injection molded plastic material of the lens array 22. In the illustrated example, stress release cuts 32 form a pattern in which some of the stress release cuts are substantially at a ninety-degree angle with respect to the other stress release cuts. Stress release cuts 32 can be formed alongside lenses 30 such that each lens (other than lenses along the periphery of the lens array) is surrounded by four stress release cuts 32. In the illustrated example, stress release cuts 32 are offset at an angle (i.e., a non-90° angle (a) such as a < 85°) with respect to the sides 34 of lens array 22. A cross-like arrangement of stress release cuts 32 can, in some cases, convert linear compression/expansion that would otherwise occur due to thermal changes into rotational movement so as to limit movement of the lens array in the lateral (x-y) directions. In some implementations, a different number of stress release cuts can be provided, and the angle of the stress release cuts can differ from the illustrated examples of FIGS. 2 and 2A.
[0024] As shown in FIG. 3, stress release cuts 32 can be provided in both the upper surface (baffle side) and lower surface (substrate side) of lens array 22. In some implementations, stress release cuts 32 may be provided in only one of the surfaces. Stress release cuts 32 can be formed, for example, by micromachining or etching the injected molded lens array 22. Alternatively, stress release cuts 32 can be formed as part of the injection molding process. For example, as indicated in FIG. 3, molds 40 for the injection molding process can include cut-out areas 42 that correspond to the areas for lenses 30, as well as projections 44 that correspond to the areas for the stress release cuts 32.
[0025] The depth of stress release cuts 32 can vary depending on the particular implementation. In some implementations, stress release cuts 32 extend only partially through the thickness of lens array 22 so as not to impact the structural stability of the lens array negatively. However, in some implementations, such as small arrays, stress release cuts 32 may extend through the entire thickness of the lens array (i.e., from the baffle-side surface to the substrate-side surface).
[0026] Instead of, or in addition to, stress release cuts 32, a frame composed of a low CTE material can be embedded within lens array 22. FIGS. 4A and 4B illustrate an implementation in which a frame 50 in the shape of a two-dimensional grid and having a low CTE is embedded within lens array 22. A portion of frame 50 is disposed around lenses 30 near the periphery of lens array 22 and other portions of the frame are disposed in regions that separate adjacent lenses 30 from one another. In this example, frame 50 is completely surrounded by the injection molded plastic material that forms lenses 30. Thus, the plastic injection molded material covers the top and bottom surfaces of frame 50.
[0027] Frame 50 can be composed, for example, of a carbon-filled plastic material, a ceramic material or a glass material. In general, frame 50 should have a linear CTE less than the linear CTE of the plastic material of lens array 22. Thus, the same polymer materials described above in connection with sidewalls 24 and baffle 28 can be used for frame 50. Likewise, the same glass and ceramic materials described above in connection with substrate 26 can be used for frame 50. Thus, even if the polymer material for lens array 22 has a relatively high linear CTE, the embedded frame 50 can have a significantly lower CTE, which can help reduce the extent of any thermal expansion and contraction as the temperature changes.
[0028] FIGS. 5A and 5B illustrate another implementation of a lens array 22 with an embedded frame 50A of a low CTE material. As in the implementation of FIGS. 4A and 4B, a portion of frame 50A is disposed around lenses 30 near the periphery of lens array 22 and other portions of frame 50A separate adjacent lenses 30 from one another.
However, in this case, the injection molded plastic material of the lens array 22 does not cover the embedded frame 50A at its upper (baffle-side) surface and its lower (substrate- side) surface. Preferably, frame 50A (or 50) is composed of a non-transparent material, which can help reduce the effects of stray light.
[0029] Instead of, or in addition to, stress release cuts 32 and/or embedded frame 50 (or 50A), polymer fibers having a low CTE can be wrapped around lens array 22. For example, as shown in FIGS. 6A and 6B, polymer fibers 60 are wrapped around the outer surface of lens array 22. In this case, polymer fibers 60 are wrapped over the upper and lower surfaces of lens array 22. In other implementations, as indicated by FIG. 6C, polymer fibers are wrapped around the side surfaces of lens array 22. In some implementations, as shown in FIG. 6D, polymer fibers 60 are wrapped over the upper and lower surfaces of lens array 22 and also are wrapped around the side surfaces of lens array 22.
[0030] Polymer fibers 60 preferably have a relatively low CTE. In general, polymer fibers 60 should have a linear CTE less than the linear CTE of the plastic material of lens array 22. Preferably, polymer fibers 60 have a linear CTE no greater than 5. For example, polymer fibers 60 can be composed of an aramid type fiber having a CTE of about -2 x 10"6/°C at a temperature of 20 °C. In other implementations, polymer fibers 60 are composed of a liquid crystal polymer fiber (e.g., VECTRAN® material) having a CTE of ±4 x 10"6/°C at a temperature of 20 °C. Other polymer fibers can be used as well. [0031] Although FIGS. 6A through 6D illustrate wrapping polymer fibers 60 around a small lens array (i.e., a 2 x 2 array), polymer fibers 60 can be wrapped around larger lens arrays as well (see, e.g., FIGS. 7A, 7B, 7C and 7D). Wrapping low CTE polymer fibers 60 around lens array 22 can help confine any lateral expansion of the lens array that may otherwise occur as a result of temperature changes. More generally, such polymer fibers 60 can be wrapped around the entire lens array 22, around portions of the array or around individual lenses 30. In such cases, polymer fibers 60 can be in direct contact with the surface(s) of lens array 22.
[0032] In addition to, or instead of, wrapping polymer fibers 60 around lens array 22 such that the polymer fibers are in direct contact with the surface(s) of lens array 22, polymer fibers 60 can be wrapped around the outside of sidewalls 24 that form the housing of lens array package 20. Thus, as shown in the example of FIG. 8, polymer fibers 60 having a low CTE are wrapped around, and are in direct contact with, the exterior surface of sidewalls 24. The same types of polymer fibers described above in connection with FIGS. 6A-6D can be used for the polymer fibers 60 of FIG. 8.
[0033] As described above, one or more features can be provided to reduce or alleviate the effects of thermal expansion/contraction of the injection molded plastic lens array material. Such features include stress release cuts in the surface(s) of the lens array, a frame having a low CTE embedded within the lens array, polymer fibers wrapped around the lens array or around the lens array housing, or a housing having sidewalls, a substrate and/or a baffle made of a low-CTE material. Each of these features can be used alone or in conjunction with one or more of the other features for reducing or alleviating the effects of the thermal expansion/contraction. The lens array packages described above can provide a lens array package that is less susceptible to problems caused by changes in temperature. Thus, more stable calibration between the lenses and the camera sub- sensors can be achieved in some cases. This, in turn, means that a camera or other image capturing device incorporating such a lens array package is more likely to be able to be used successfully over a wider range of temperature. [0034] In some implementation, the array can take the form of a IxN array, an NxM (linear or rectangular) array, a triangular array or an array with some other arrangement. Such arrays may be applicable, for example, to various ones of the embodiments described above (e.g., FIGS. 1, 2, 4A, 4B, 5A, 5B, 6C, 7C and 8).
[0035] Other implementations are within the scope of the claims.

Claims

What is claimed is:
1. A lens array package comprising:
a lens array; and
a housing for the lens array, the housing including sidewalls and a substrate; wherein the sidewalls are composed of a first material having a linear constant of thermal expansion of no more than 15 x lO^C at 20 °C.
2. The lens array package of claim 1 wherein the first material includes a polymer.
3. The lens array package of claim 2 wherein the first material includes a carbon filler.
4. The lens array package of claim 2 wherein the first material includes a carbon reinforced polycarbonate.
5. The lens array package of claim 2 wherein the first material includes a ceramic filler.
6. The lens array package of claim 5 wherein the ceramic filler includes aluminum.
7. The lens array package of claim 5 wherein the ceramic filler includes zirconium.
8. The lens array package of any preceding claim wherein the sidewalls are composed of a non-transparent material.
9. The lens array package of any preceding claim wherein the lens array is attached to the sidewalls.
10. The lens array package of any preceding claim wherein the substrate is composed of glass or ceramic material having a linear constant of thermal expansion of no more than 15 x l0"6/°C at 20 °C.
11. The lens array package of any preceding claim wherein the substrate is composed of borosilicate.
12. The lens array package of any preceding claim further including a baffle, wherein the baffle is on one side of the lens array and the substrate is on a different side of the lens array, and wherein the baffle is composed of a second material having a linear constant of thermal expansion of no more than 15 x l(r6/oC at 20 °C.
13. The lens array package of claim 12 wherein the second material includes a polymer.
14. The lens array package of claim 13 wherein the second material includes a carbon filler.
15. The lens array package of claim 13 wherein the second material includes a carbon reinforced polycarbonate.
16. The lens array package of claim 13 wherein the second material includes a ceramic filler.
17. The lens array package of claim 16 wherein the ceramic filler of the second material includes aluminum.
18. The lens array package of claim 16wherein the ceramic filler of the second material includes zirconium.
19. The lens array package of any preceding claim wherein the baffle is composed of a non-transparent material.
20. A lens array comprising:
a plurality of lenses,
wherein the lens array is composed of a plastic material having stress release cuts in its surface.
21. The lens array of claim 20 including at least two stress release cuts adjacent each of the lenses.
22. The lens array of claim 20 or claim 21 wherein at least some of the stress release cuts are oriented substantially perpendicular to one another.
23. The lens array of any one of claims 20 - 22 wherein there are at least four stress release cuts around some of the lenses.
24. The lens array of any one of claims 20 - 23 wherein each stress release cut forms an angle of less than 90° with respect to a side of the lens array.
25. The lens array of any one of claims 20 - 24 wherein there are stress release cuts in opposite surfaces of the lens array.
26. The lens array of any one of claims 20 - 25 wherein the lens array is an injection molded plastic lens array.
27. The lens array of any one of claims 20 - 26 wherein the stress release cuts form a cross-like arrangement in the surface of the plastic material.
28. A lens array comprising:
a plurality of lenses,
wherein the lens array is composed of a plastic material and has an embedded grid-like frame in regions that separates adjacent lenses from one another, and wherein the frame has a constant o f thermal expansion that is lower than a constant of thermal expansion of the plastic material of the lens array.
29. The lens array of claim 28 wherein the frame is composed of a polymer material.
30. The lens array of claim 29 wherein the polymer material has a linear constant of thermal expansion of no more than 15 x 10"6/°C at 20 °C.
31. The lens array of claim 30 wherein the polymer material includes a carbon filler.
32. The lens array of claim 30 wherein the polymer material includes a carbon reinforced polycarbonate.
33. The lens array of claim 30 wherein the polymer material includes a ceramic filler.
34. The lens array of claim 33 wherein the ceramic filler includes aluminum.
35. The lens array of claim 33 wherein the ceramic filler includes zirconium.
36. The lens array of claim 38 wherein the frame is composed of a glass or ceramic material.
37. The lens array of claim 36 wherein the glass or ceramic material has a linear constant of thermal expansion of no more than 15 x 10"6/°C at 20 °C.
38. The lens array of claim 37 wherein the frame is composed of borosilicate.
39. The lens array of claim 37 wherein the frame is composed of alumina.
40. A lens array comprising:
a plurality of lenses, wherein the lens array is composed of a plastic material; and polymer fibers wrapped around an outer surface of the lens array.
41. The lens array of claim 40 wherein the polymer fibers have a constant of thermal expansion less than a constant of thermal expansion of the plastic material of the lens array.
42. The lens array of claim 41 wherein the constant of thermal expansion of the polymer fibers is no greater than five.
43. The lens array of claim 41 wherein the polymer fibers are composed of an aramid type fiber.
44. The lens array of claim 41 wherein the polymer fibers are composed of a liquid crystal polymer fiber.
45. The lens array of any one of claims 40 - 44 including polymer fibers wrapped around outer surfaces of the lens array in at least two planes that are substantially orthogonal to one another.
46. The lens array of any one of claims 40 - 45 wherein the lens array is composed of an injection molded plastic material.
47. A lens array package comprising:
a lens array comprising a plurality of lenses, wherein the lens array is composed of a plastic material; a housing for the lens array, wherein the lens array is attached to inner surfaces of the housing; and
polymer fibers wrapped around an outer surface of the housing.
48. The lens array package of claim 47 wherein the polymer fibers have a constant of thermal expansion less than a constant of thermal expansion of the plastic material of the lens array.
49. The lens array package of claim 48 wherein the constant of thermal expansion of the polymer fibers is no greater than five.
50. The lens array package of claim 48 wherein the polymer fibers are composed of an aramid type fiber.
51. The lens array package of claim 48 wherein the polymer fibers are composed of a liquid crystal polymer fiber.
52. A lens array package comprising:
a lens array comprising a plurality of lenses, wherein the lens array is composed of an injection molded plastic material;
a housing for the lens array, wherein the housing includes sidewalls and a substrate, wherein the lens array is attached to inner surfaces of the sidewalls; and
means for reducing or alleviating effects of thermal expansion and/or contraction of the injection molded plastic material of the lens array.
53. An image capturing device comprising:
a lens array package as recited in any one of the previous claims; and
optoelectronic sensors positioned to detect light passing through the lens array.
PCT/SG2014/000159 2013-04-12 2014-04-11 Lens array packages and image capturing devices incorporating the same WO2014168586A1 (en)

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