PATENT DOCUMENT

Publication Number: US-11340388-B2
Application Number: US-201916551521-A
Country: US
Kind Code: B2

Title: Power prism for folded lenses

Abstract:
An optical power prism that may be used in folded lens systems that consists of a glass prism and a glass lens attached to a surface of the prism using a thin layer of optical glue or by optical contact. The glass lens does not have a flange and thus the prism can be smaller than prisms used in conventional power prisms with the same lens effective area, thus reducing the Z-height of the power prism when compared to conventional power prisms. An optical glass may be used for the lens that has a higher refractive index than can be provided by optical plastic which allows the lens to be thinner than plastic lenses. The lenses may be formed by molding a glass wafer to form lens shapes on a first surface of the wafer; the molded wafer is then ground from a second surface to singulate the lenses.

Claims:
What is claimed is: 
     
       1. An optical power prism, comprising:
 a prism that includes an object side surface, a reflective surface, and an image-side surface; and 
 a glass lens, wherein one side of the glass lens is planar and is attached to a planar surface of the prism; 
 wherein width of an effective area of the glass lens is the same as diameter of the glass lens at the planar surface of the prism, and the effective area of the glass lens is smaller than an area of the surface of the prism to which the glass lens is attached. 
 
     
     
       2. The optical power prism as recited in  claim 1 , wherein the glass lens is composed of a glass material with an Abbe number that is &gt;45. 
     
     
       3. The optical power prism as recited in  claim 1 , wherein the prism is composed of an optical glass material with a higher refractive index than a glass material used in the glass lens. 
     
     
       4. The optical power prism as recited in  claim 1 , wherein the glass lens is composed of an optical glass material with a refractive index that is &gt;1.5. 
     
     
       5. The optical power prism as recited in  claim 1 , wherein the prism is composed of an optical glass material with a refractive index that is &gt;1.7 to provide total internal reflection at the reflective surface of the prism. 
     
     
       6. The optical power prism as recited in  claim 1 , wherein Z-axis height of the power prism is within a range of 3 millimeters to 7 millimeters. 
     
     
       7. The optical power prism as recited in  claim 1 , wherein the glass lens is attached to the surface of the prism using an optical glue or by optical contact. 
     
     
       8. The optical power prism as recited in  claim 1 , wherein the glass lens is attached to the object side surface of the prism. 
     
     
       9. The optical power prism as recited in  claim 1 , wherein the glass lens is attached to the image side surface of the prism. 
     
     
       10. The optical power prism as recited in  claim 1 , wherein the glass lens is attached to the object side surface of the prism, and wherein a second glass lens is attached to the image side surface of the prism. 
     
     
       11. The optical power prism as recited in  claim 1 , wherein the glass lens is a plano-convex lens. 
     
     
       12. The optical power prism as recited in  claim 1 , wherein the glass lens is a plano-concave lens. 
     
     
       13. The optical power prism as recited in  claim 1 , wherein the glass lens is a plano-convex lens, wherein the glass lens is attached to the object side surface of the prism, and wherein an aperture stop is located at an outer edge of the glass lens. 
     
     
       14. A lens system, comprising:
 a plurality of elements arranged along a folded optical axis of the lens system, wherein the plurality of elements includes, in order along the folded optical axis from an object side of the lens system to an image side of the lens system:
 a power prism that redirects light received from an object field from a first portion of the folded optical axis to a second portion of the folded optical axis, wherein the power prism includes:
 a glass prism that includes an object side planar surface, a reflective surface, and an image-side surface; and 
 a glass lens, wherein one side of the glass lens is planar and is attached to the object side planar surface of the prism, wherein width of an effective area of the glass lens is the same as diameter of the glass lens at the object side planar surface of the prism, wherein the diameter of the glass lens is smaller than an extent of the object side planar surface of the prism; and 
 
 a lens stack comprising one or more refractive lens elements that refract light on the second portion of the folded optical axis to form an image at an image plane. 
 
 
     
     
       15. The lens system as recited in  claim 14 , further comprising a prism located on the image side of the lens stack that redirects light received from the lens stack from the second portion of the folded optical axis to a third portion of the folded optical axis. 
     
     
       16. The lens system as recited in  claim 14 , wherein the glass lens is a plano-convex lens. 
     
     
       17. The lens system as recited in  claim 14 , further comprising an aperture stop located at an outer edge of the glass lens. 
     
     
       18. The lens system as recited in  claim 14 , wherein the glass lens is composed of an optical glass material with a refractive index that is &gt;1.5, and wherein the prism is composed of an optical glass material with a refractive index that is &gt;1.7 to provide total internal reflection at the reflective surface of the prism. 
     
     
       19. A camera, comprising:
 an image sensor configured to capture light projected onto a surface of the image sensor; 
 a power prism that redirects light received from an object field from a first portion of an optical axis to a second portion of the optical axis, wherein the power prism includes:
 a glass prism that includes an object side planar surface, a reflective surface, and an image-side surface; and 
 a glass lens, wherein one side of the glass lens is planar and is attached to the object side planar surface of the prism, wherein width of an effective area of the glass lens is the same as diameter of the glass lens at the object side planar surface of the prism, wherein the diameter of the glass lens is smaller than an extent of the object side planar surface of the prism; and 
 
 one or more refractive lens elements that refract light on the second portion of the optical axis to form an image at an image plane at or near a surface of the image sensor. 
 
     
     
       20. The camera as recited in  claim 19 , further comprising a prism located between the one or more refractive lens elements and the image sensor that redirects light received from the one or more refractive lens elements from the second portion of the folded optical axis to a third portion of the folded optical axis.

Description:
PRIORITY INFORMATION 
     This application claims benefit of priority of U.S. Provisional Application Ser. No. 62/726,163 entitled “POWER PRISM FOR FOLDED LENSES” filed Aug. 31, 2018, the content of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     This disclosure relates generally to camera systems, and more specifically to power prisms for folded lens systems. 
     Description of the Related Art 
     The advent of small, mobile multipurpose devices such as smartphones and tablet or pad devices has resulted in a need for high-resolution, small form factor cameras that are lightweight, compact, and capable of capturing high resolution, high quality images at low F-numbers for integration in the devices. However, due to limitations of conventional camera technology, conventional small cameras used in such devices tend to capture images at lower resolutions and/or with lower image quality than can be achieved with larger, higher quality cameras. Achieving higher resolution with small package size cameras generally requires use of an image sensor with small pixel size and a good, compact imaging lens system. Advances in technology have achieved reduction of the pixel size in image sensors. However, as image sensors become more compact and powerful, demand for compact imaging lens systems with improved imaging quality performance has increased. In addition, there are increasing expectations for small form factor cameras to be equipped with higher pixel count and/or larger pixel size image sensors (one or both of which may require larger image sensors) while still maintaining a module height that is compact enough to fit into portable electronic devices. Thus, a challenge from an optical system design point of view is to provide an imaging lens system that is capable of capturing high brightness, high resolution images under the physical constraints imposed by small form factor cameras. 
     SUMMARY OF EMBODIMENTS 
     Embodiments of an optical prism with refractive power for folded lens systems are described that may, for example, be used in small form factor cameras in mobile multipurpose devices such as smartphones and tablet or pad devices. A folded lens system may include one or more prisms and a lens stack including one or more refractive lens elements. A first prism redirects light from a first optical axis to a second optical axis to thus provide a “folded” optical axis for the lens system. Using a prism to fold the optical axis may, for example, reduce the Z-height of the lens system, and thus may reduce the Z-height of a camera that includes the lens system. In some folded lens systems, a second prism may be located at the image side of the lens stack to fold the optical axis on to a third axis. 
     In some folded lens systems, a prism with refractive power (referred to as a power prism) may be used. For example, in some camera designs, a folded lens system may require a lens on the object side of the first prism. Instead of using a separate lens on the object side of the prism, a power prism composed of a prism and a lens deposited on or attached to the object side surface of the prism may be used. An advantage of the power prism is that the convex object side surface of the lens can be positioned closer to the surface of the prism than can be done using a separate lens, thus reducing Z-height of the folded lens system. 
     Conventionally, power prisms for folded lens systems are formed using a replication process in which a plastic material is deposited on a surface of a prism, formed into a lens shape, and cured using UV light, or alternatively using a process in which a plastic lens is formed using an injection molding process and attached to a surface of the prism. However, these conventional processes cause a flange to be formed around the plastic lens, which requires the surface of the prism to be large enough to accommodate the flange. The size of the surface of the prism to which the lens is attached dictates the size of the prism. As the dimensions of the surface of the prism on which the plastic lens with flange is attached increase, the Z-height of the prism, and thus the Z-height of the power prism including the lens, increases. 
     Embodiments of a power prism are described that may be used in folded lens systems. The power prism consists of a glass prism and a glass lens attached to a surface of the prism using optical glue or by optical contact. The glass lens does not have a flange. Since the glass lens does not have a flange, the dimensions of the prism to which the glass lens is attached can be smaller than the dimensions of a prism to which a plastic lens with flange is attached. Since the dimensions of the surface of the prism to which the glass lens is attached are decreased, the Z-height of the prism, and thus the Z-height of the power prism including the lens, is decreased. Thus, embodiments of the power prism described herein may provide reduced Z-height when compared to power prisms formed using conventional methods. 
     Further, eliminating the flange allows the glass lenses to be thinner than the plastic lenses formed by conventional methods. In addition, a glass material may be used for the lens of the power prism that has a higher refractive index than can be provided by the plastic material used in conventional methods. The higher refractive index allows the glass lenses to be thinner than the plastic lenses formed by conventional methods. Thus, in addition to reducing Z-height of the power prism by reducing Z-height of the prism, embodiments of the power prism described herein may also reduce Z-height by reducing thickness of the lens. 
     Embodiments of a method of manufacturing power prisms are described in which the glass lenses are formed by a process in which a glass wafer is molded to form lens shapes on a first surface of the wafer, and the molded wafer is then ground from a second surface to singulate or separate the glass lenses. The glass lenses thus formed do not have flanges. The singulated glass lenses are then attached to the surfaces of glass prisms using a thin layer of optical glue or by optical contact to form the power prisms. In embodiments that use optical glue to attach the lens to the prism, thickness of the glue, and thus spacing between the plano surface of the lens and the surface of the prism may be &lt;10 microns. In embodiments that use optical contact to attach the lens to the prism, spacing between the plano surface of the lens and the surface of the prism may be &lt;5 microns. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a camera with a folded lens system, according to some embodiments. 
         FIG. 2  illustrates a conventional power prism formed by a process that deposits a plastic lens on a surface of a prism. 
         FIG. 3  illustrates a power prism formed by attaching a singulated glass lens to a surface of a prism, according to some embodiments. 
         FIGS. 4A through 4D  compare a power prism as illustrated in  FIG. 3  to a power prism as illustrated in  FIG. 2 , according to some embodiments. 
         FIGS. 5A through 5G  illustrate a method of manufacture for a power prism as illustrated in  FIG. 3 , according to some embodiments. 
         FIGS. 6A through 6F  illustrate various alternative embodiments of a power prism as illustrated in  FIG. 3 . 
         FIGS. 7A through 7D  illustrate various embodiments of cameras with folded lens systems that include at least one power prism. 
         FIG. 8  is a flowchart of a method for capturing images using embodiments of a folded lens system that includes a power prism, according to some embodiments. 
         FIG. 9  is a flowchart of a method for manufacturing a power prism as illustrated in  FIG. 3 , according to some embodiments. 
         FIG. 10  illustrates an example computer system. 
     
    
    
     This specification includes references to “one embodiment” or “an embodiment.” The appearances of the phrases “in one embodiment” or “in an embodiment” do not necessarily refer to the same embodiment. Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure. 
     “Comprising.” This term is open-ended. As used in the appended claims, this term does not foreclose additional structure or steps. Consider a claim that recites: “An apparatus comprising one or more processor units . . . ”. Such a claim does not foreclose the apparatus from including additional components (e.g., a network interface unit, graphics circuitry, etc.). 
     “Configured To.” Various units, circuits, or other components may be described or claimed as “configured to” perform a task or tasks. In such contexts, “configured to” is used to connote structure by indicating that the units/circuits/components include structure (e.g., circuitry) that performs those task or tasks during operation. As such, the unit/circuit/component can be said to be configured to perform the task even when the specified unit/circuit/component is not currently operational (e.g., is not on). The units/circuits/components used with the “configured to” language include hardware—for example, circuits, memory storing program instructions executable to implement the operation, etc. Reciting that a unit/circuit/component is “configured to” perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112(f), for that unit/circuit/component. Additionally, “configured to” can include generic structure (e.g., generic circuitry) that is manipulated by software and/or firmware (e.g., an FPGA or a general-purpose processor executing software) to operate in manner that is capable of performing the task(s) at issue. “Configure to” may also include adapting a manufacturing process (e.g., a semiconductor fabrication facility) to fabricate devices (e.g., integrated circuits) that are adapted to implement or perform one or more tasks. 
     “First,” “Second,” etc. As used herein, these terms are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical, etc.). For example, a buffer circuit may be described herein as performing write operations for “first” and “second” values. The terms “first” and “second” do not necessarily imply that the first value must be written before the second value. 
     “Based On.” As used herein, this term is used to describe one or more factors that affect a determination. This term does not foreclose additional factors that may affect a determination. That is, a determination may be solely based on those factors or based, at least in part, on those factors. Consider the phrase “determine A based on B.” While in this case, B is a factor that affects the determination of A, such a phrase does not foreclose the determination of A from also being based on C. In other instances, A may be determined based solely on B. 
     DETAILED DESCRIPTION 
     Embodiments of an optical prism with refractive power for folded lens systems are described that may, for example, be used in small form factor cameras in mobile multipurpose devices such as smartphones and tablet or pad devices. A folded lens system may include one or more prisms and a lens stack including one or more refractive lens elements. A first prism redirects light from a first optical axis to a second optical axis to thus provide a “folded” optical axis for the lens system. Using a prism to fold the optical axis may, for example, reduce the Z-height of the lens system, and thus may reduce the Z-height of a camera that includes the lens system. In some embodiments, a second prism may be located at the image side of the lens stack to fold the optical axis on to a third axis. 
     In some folded lens systems, a prism with refractive power (referred to as a power prism) may be used. For example, in some camera designs, a folded lens system may require a lens on the object side of the first prism. Instead of using a separate lens on the object side of the prism, a power prism composed of a prism and a lens deposited on or attached to the object side surface of the prism may be used. An advantage of the power prism is that the convex object side surface of the lens can be positioned closer to the surface of the prism than can be done using a separate lens, thus reducing Z-height of the folded lens system. 
     Conventionally, power prisms for folded lens systems are formed using a replication process in which a plastic material is deposited on a surface of a prism, formed into a lens shape, and cured using UV light, or alternatively using a process in which a plastic lens is formed using an injection molding process and attached to a surface of the prism. However, these conventional processes cause a flange to be formed around the plastic lens, which requires the surface of the prism to be large enough to accommodate the flange. The size of the surface of the prism on which the lens is attached dictates the size of the prism. As the dimensions of the surface of the prism on which the plastic lens with flange is attached increase, the Z-height of the prism, and thus the Z-height of the power prism including the lens, increases. A goal in small form factor cameras is to reduce Z-height of the cameras for use in thin mobile multipurpose devices. A limiting factor on Z-height in conventional folded lens systems is the Z-height of these conventional power prisms. 
     An optical prism with refractive power (referred to herein as a power prism) is described that may be used in folded lens systems. The power prism consists of a glass prism and a glass lens attached to a surface of the prism. In some embodiments, instead of using a replication process or injection molding process to form a plastic lens for a power prism, a process is used in which a glass wafer is molded to form lens shapes on a first surface of the wafer, and the molded wafer is then ground from a second surface to singulate or separate the glass lenses. The glass lenses thus formed do not have flanges. The singulated glass lenses are then attached to the surfaces of glass prisms using a thin layer (&lt;10 microns) of optical glue or by optical contact. Since the glass lenses do not have flanges, the surface of the prisms to which the glass lenses are attached can be smaller than the prisms used in conventional power prisms as described above, and the power prisms formed by attaching the glass lenses to the prisms are smaller than the conventional power prisms described above. Since the dimensions of the surface of the prism to which the glass lens is attached are decreased, the Z-height of the prism, and thus the Z-height of the power prism including the lens, is decreased. 
     In addition to reducing the size of the prism by eliminating the added width of the flange, eliminating the thickness of the flange allows the glass lenses to be thinner than the plastic lenses formed by conventional methods. In addition, a glass material may be used for the lens that has a higher refractive index than can be provided by the plastic material used to form lenses in conventional methods. The higher refractive index allows the glass lenses to be thinner than the plastic lenses formed by the conventional methods. 
     The prism and lens may be composed of optical glass. In some embodiments, the prism and lens may be composed of the same glass material. However, in some embodiments, the prism and lens may be composed of different glass materials. In some embodiments, the lens may be composed of a glass material with an Abbe number that is &gt;45 to correct for color aberrations. In some embodiments, the prism may be composed of a glass material with a higher refractive index than the glass material used in the lens. In some embodiments, the lens may be composed of a glass material with a refractive index that is &gt;1.5. In some embodiments, the prism may be composed of a glass material with a refractive index that is &gt;1.7 to provide total internal reflection at the sloped reflective surface of the prism. 
     While embodiments of a power prism with a glass lens attached to the object side of a prism are described, in some embodiments a glass lens may instead or also be attached to the image side of a prism to form a power prism for use in a folded lens system. Further, while embodiments of a plano-convex glass lens attached to a prism are described, plano-concave or other types of lenses with a planar surface may also be attached to a prism. Note that the planar surface of a lens is attached to a surface of the prism. 
       FIG. 1  illustrates a camera that includes a folded lens system with a power prism, according to some embodiments.  FIG. 1  illustrates components of a camera  100  that includes a folded lens system with two prisms  120  and  140  with one or more refractive lenses  132  (three lenses  132 A,  132 B, and  132 C, in this example) located in a lens barrel  130  between prisms  120  and  140 . The prisms  120  and  140  provide a “folded” optical axis for the camera  100 . A reflective surface  122  of a first prism  120  redirects light from an object field from a first axis (AX 1 ) to the lenses  132  on a second axis (AX 2 ). The lenses  132  refract the light to a reflective surface  142  of a second prism  140  that redirects the light onto a third axis (AX 3 ) on which an image sensor  160  of the camera  100  is disposed. The redirected light forms an image at an image plane at or near the surface of the image sensor  160 . The camera  100  may, but does not necessarily, include an infrared (IR) filter  150 , for example located between the second prism  140  and the image sensor  160 . The camera  100  may also include an aperture stop  112 , for example located on the object side of the first prism  120 . The number, shapes, materials, and arrangements of the refractive lens elements  132  in the lens barrel  130  may be selected according to the requirements of the particular camera  100 . 
     As shown in the example camera  100  of  FIG. 1 , in some folded lens systems, a prism with refractive power (referred to as a power prism  190 ) may be used. In this example, to form the power prism  190 , a lens  110  has been deposited on the object side of prism  120  using a replication process in which a plastic material is deposited on a surface of prism  120 , formed into a lens shape, and cured using UV light. Alternatively, to form the power prism  190 , a plastic lens  110  may be formed using an injection molding process and attached to a surface of the prism  120 . However, these processes causes a flange  114  to be formed around the plastic lens  110 , which requires the surface of the prism  120  to be large enough to accommodate the flange  114 . The size of the surface of the prism  120  on which the lens  110  is attached dictates the size of the prism  120 . As the dimensions of the surface of the prism  120  on which the lens  110  is attached increase, the Z-height of the prism  120 , and thus the Z-height of the power prism  190  including the lens  110 , increases. A goal in small form factor cameras is to reduce Z-height of the cameras for use in thin mobile multipurpose devices. A limiting factor on Z-height in conventional folded lens systems is the Z-height of these conventional power prisms  190 . 
       FIG. 2  illustrates a conventional power prism  190  formed by a replication process that deposits a plastic lens  110  (referred to as a plastic lens) on a surface of a prism  120 , or alternatively using a process in which a plastic lens  110  is formed using an injection molding process and attached to a surface of the prism  120 .  FIG. 2  shows a side view (A) and a top view (B) of the power prism  190 . As can be seen in  FIG. 2 , the process forms a flange  114  around the effective area  112  of the plastic lens  110 . The effective area of a lens may be defined by the effective diameter of the lens. In optics, the effective diameter of a lens may be defined as twice the distance from the geometric center of the lens to the edge of the lens shape (in this example, a plano-convex lens shape). In an optical system including an aperture and a sensor, the aperture and focal length of the optical system determine the cone angle of a bundle of rays that come to a focus at an image plane at or near the sensor. The effective area of a lens in the optical system is or contains the region of the lens in which ray bundles limited by the aperture are affected by the lens. The flange  114  extends outwards from the edge of the lens  110  shape. In addition, a margin  116  may be required around the flange  114  to accommodate slight variations in the manufacturing process. The total diameter of the lens  110  is the width  118  at the flange  114  (i.e., the effective diameter of the lens  110  plus twice the width of the flange  114 ). The width  118  of the lens  110  at the flange  114  requires the surface of the prism  120  on which the lens  110  is attached to be large enough to accommodate the flange  114  plus the margin  116 . The size of the surface of the prism  120  on which the lens  110  is attached dictates the size of the prism  120 . As the dimensions of the surface of the prism  120  on which the plastic lens  110  is attached increase, the Z-height of the prism  120 , and thus the Z-height of the power prism  190 , increases. As a non-limiting example, prism  120  may have a Z-axis height of about 4 mm, and plastic lens  110  may have a total thickness of about 0.6 mm (including the thickness of the flange  114 , e.g. 0.1 mm), for a total Z-axis height for power prism  190  of 4.6 mm. 
       FIG. 3  illustrates a power prism  390  formed by attaching a singulated glass lens  370  to a surface of a prism  380 , according to some embodiments.  FIG. 3  shows a side view (A) and a top view (B) of the power prism  390 . As can be seen in  FIG. 3 , glass lens  370  is formed by a process that does not form a flange around the effective area  312  of the lens  370 . An example method for forming glass lens  370  is illustrated in  FIGS. 5A-5D  and  FIG. 9 . The glass lens  370  may be attached to the prism  380  using a thin layer (&lt;10 microns) of optical glue or by optical contact, as illustrated in  FIGS. 5E-5G  and  FIG. 9 . A margin  316  may be required around the lens  370  to accommodate slight variations in the manufacturing process. Since lens  370  does not have a flange, the diameter of the lens  370  is the width of the effective area  312  of the lens  370  (i.e., the lens effective diameter). By eliminating the flange, the surface of the prism  380  to which the glass lens  370  is attached can be smaller than the surface of the prism  120  on which a plastic lens  110  with the same effective area as glass lens  370  is deposited using a process as shown in  FIG. 2 . The size of the surface of the prism  120  on which the lens  110  is deposited dictates the size of the prism  120 . Since the dimensions of the surface of the prism  380  to which the glass lens  370  is attached are decreased, the Z-height of the prism  380 , and thus the Z-height of the power prism  390 , is decreased when compared to the power prism  190  of  FIG. 2 . 
     In addition to reducing the Z-height of the prism  380  by eliminating the added width of the flange, eliminating the thickness of the flange may allow the glass lens  370  to be thinner than the plastic lens  110  formed by conventional methods. In addition, a glass material may be used for the lens  370  that has a higher refractive index than can be provided by the plastic material used to form lens  110 . The higher refractive index allows the glass lens  370  to be thinner than the plastic lens  110  formed by conventional methods. 
     The prism  380  and lens  370  may be composed of optical glass. In some embodiments, the prism  380  and lens  370  may be composed of the same glass material. However, in some embodiments, the prism  380  and lens  370  may be composed of different glass materials. In some embodiments, the lens  370  may be composed of a glass material with an Abbe number that is &gt;45 to correct for color aberrations. In some embodiments, the prism  380  may be composed of a glass material with a higher refractive index than the glass material used in the lens  370 . In some embodiments, the lens  370  may be composed of a glass material with a refractive index that is &gt;1.5. In some embodiments, the prism  380  may be composed of a glass material with a refractive index that is &gt;1.7 to provide total internal reflection at the sloped reflective surface of the prism. 
       FIGS. 4A through 4D  compare a power prism  390  as illustrated in  FIG. 3  to a power prism  190  as illustrated in  FIG. 2 , according to some embodiments. 
       FIG. 4A  shows a side view of power prism  190  and power prism  390 . As can be seen in  FIG. 4A , eliminating flange  114  allows a smaller prism  380  to be used in power prism  390  than the prism  120  used in power prism  190 . Further, as can be seen in  FIG. 4A , eliminating the thickness of the flange  114  allows the glass lens  370  to be thinner than the plastic lens  110  formed by conventional methods. In addition, a glass material may be used for the lens  370  that has a higher refractive index than can be provided by the plastic material used to form lens  110 , which allows the glass lens  370  to be thinner than the plastic lens  110  formed by conventional methods.  FIG. 4A  shows the reduction in Z-height of power prism  390  when compared to power prism  190  due to the elimination of the flange  114  width, and also shows the reduction in Z-height of power prism  390  when compared to power prism  190  due to elimination of the thickness of the flange  114  combined with the higher refractive index of the glass material used in glass lens  370 . 
     As a non-limiting example, prism  120  may have a Z-axis height of about 4 mm, and plastic lens  110  may have a total thickness of about 0.6 mm (including the thickness of the flange  114 ), for a total Z-axis height for power prism  190  of 4.6 mm. The total width of the flange  114  may be about 0.45 millimeters (mm) (0.225 mm on each side of the effective area), and thickness of the flange  114  may be about 0.1 mm. Eliminating the width of the flange  114  may allow the Z-axis height of prism  380  (and thus the Z-axis height of power prism  390 ) to be reduced by about 0.45 mm. Thus, the Z-axis height of prism  380  may be about 3.55 mm. Eliminating the thickness of the flange  114  may allow the thickness of lens  370  (and thus the Z-axis height of power prism  390 ) to be reduced by 0.1 mm. The higher refractive index of the glass material used in glass lens  370  may allow the thickness of lens  370  (and thus the Z-axis height of power prism  390 ) to be reduced by an additional 0.03 mm. Total reduction on the Z-axis is thus about 0.58 mm. Thus, Z-axis height of power prism  390  may be approximately 4.0 mm. Note, however, that power prisms  390  with larger or smaller Z-axis heights (e.g., within a range of 3 mm to 7 mm) may be provided. 
       FIG. 4B  shows a side view of power prism  190  and power prism  390 . As can be seen in  FIG. 4B , eliminating flange  114  allows a smaller prism  380  to be used in power prism  390  than the prism  120  used in power prism  190 . In addition to reducing Z-height of the prism  390 , eliminating the flange  114  also allows the prism  380  to be reduced in the other (X and Y axes) dimensions. 
       FIGS. 4C and 4D  show a top view of power prism  190  and power prism  390 . As can be seen in  FIG. 4C , eliminating flange  114  allows the surface of prism  380  to which glass lens  370  is attached to be smaller than the surface of prism  120  on which plastic lens  110  is deposited while providing the same size effective area  312  in glass lens  370  as the effective area  112  of plastic lens  110 . As can be seen in  FIG. 4D , eliminating flange  114  reduces the extended width needed for prism  380 . For prism  120 , the extended width on one side is equal to the width of the flange plus the width of the margin. The total extended width is thus 2 * (flange width+margin width). Given a flange width of 0.225 mm and a margin width of 0.05 mm, the total extended width for prism  120  is &gt;0.5 mm. For prism  380 , the total extended width is 2 * margin width. Given a margin width of 0.05 mm, the total extended width for prism  380  is 0.1 mm, or more generally &lt;0.2 mm. Eliminating the flange  114  also allows the prism  380  to be reduced in X, Y and Z dimensions. Since the dimensions of prism  380  to which the glass lens  370  is attached are decreased, the Z-height of the power prism  390  is decreased when compared to the power prism  190 . 
       FIGS. 5A through 5G  illustrate a method of manufacture for a power prism as illustrated in  FIG. 3 , according to some embodiments. In this method, the glass lenses are formed by a process in which a glass wafer is molded to form lens shapes on a first surface of the wafer, and the molded wafer is then ground from a second surface to singulate or separate the glass lenses. The glass lenses thus formed do not have flanges. The singulated glass lenses are then attached to the surfaces of glass prisms using a thin layer of optical glue or by optical contact to form the power prisms. In embodiments that use optical glue to attach the lens to the prism, thickness of the glue, and thus spacing between the plano surface of the lens and the surface of the prism may be &lt;10 microns. In embodiments that use optical contact to attach the lens to the prism, spacing between the plano surface of the lens and the surface of the prism may be &lt;5 microns. 
     In  FIG. 5A , an optical glass wafer  510 A is positioned between a top mold  500 A and a bottom mold  500 B. In  FIG. 5B , the wafer  510 A is pressed between molds  500 A and  500 B to form a molded glass wafer  510 B that has the desired lens shapes on a first surface of the wafer  510 B as shown in  FIG. 5C . In  FIG. 5D , the molded wafer  510 B is positioned in a precision grinding and polishing mechanism  520  where it is ground and polished from a second surface to singulate or separate convex-plano glass lenses  570  as shown in  FIG. 5E . In  FIG. 5F , the singulated convex-plano glass lenses  570  are attached to a surface of glass prisms  580  using a thin layer (&lt;10 microns) of optical glue or by optical contact to form power prisms  590  as shown in  FIG. 5G . In some embodiments, an anti-reflective coating may be applied to at least one surface of the glass lenses prior to singulation by grinding, or alternatively after singulation. 
     The prisms  580  and lenses  570  may be composed of optical glass. In some embodiments, the prisms  580  and lenses  570  may be composed of the same glass material. However, in some embodiments, the prisms  580  and lenses  570  may be composed of different glass materials. In some embodiments, the lenses  570  may be composed of a glass material with an Abbe number that is &gt;45 to correct for color aberrations. In some embodiments, the prisms  580  may be composed of a glass material with a higher refractive index than the glass material used in the lens. In some embodiments, the lenses  570  may be composed of a glass material with a refractive index that is &gt;1.5. In some embodiments, the prisms  580  may be composed of a glass material with a refractive index that is &gt;1.7 to provide total internal reflection at the sloped reflective surface of the prism. 
       FIGS. 6A through 6F  illustrate various alternative embodiments of a power prism as illustrated in  FIG. 3 . While embodiments of a power prism with a glass lens attached to the object side of a prism are generally described, in some embodiments a glass lens may instead or also be attached to the image side of a prism to form a power prism for use in a folded lens system. Further, while embodiments of a plano-convex glass lens with positive refractive power attached to a prism are described, plano-concave or other types of lenses may also be attached to a prism. 
       FIG. 6A  shows a power prism  690 A that consists of a plano-convex glass lens with positive refractive power attached to the object side of a prism. As shown in  FIG. 6A , in some embodiments, the aperture stop may be located at the outer edge of the lens.  FIG. 6B  shows a power prism  690 B that consists of a plano-convex glass lens with positive refractive power attached to the image side of a prism.  FIG. 6C  shows a power prism  690 C that consists of a concave glass lens with negative refractive power attached to the object side of a prism.  FIG. 6D  shows a power prism  690 D that consists of a concave glass lens with negative refractive power attached to the image side of a prism.  FIG. 6E  shows a power prism  690 E that consists of a plano-convex glass lens with positive refractive power attached to the object side of a prism and a plano-convex glass lens with positive refractive power attached to the image side of the prism.  FIG. 6F  shows a power prism  690 F that consists of a plano-convex glass lens with positive refractive power attached to the object side of a prism and a concave glass lens with negative refractive power attached to the image side of the prism. 
       FIGS. 7A through 7D  illustrate various embodiments of cameras with folded lens systems that include at least one power prism as illustrated in  FIGS. 6A through 6F .  FIG. 7A  shows a camera  700 A that includes, from an object side to an image side, a power prism  790 , a lens barrel  730  containing one or more refractive lens elements, a standard prism  740 , and an image sensor  760 .  FIG. 7B  shows a camera  700 B that includes, from an object side to an image side, a power prism  790 , a lens barrel  730  containing one or more refractive lens elements, and an image sensor  760 .  FIG. 7C  shows a camera  700 C that includes, from an object side to an image side, a standard prism  740 , a lens barrel  730  containing one or more refractive lens elements, a power prism  790 , and an image sensor  760 .  FIG. 7D  shows a camera  700 D that includes, from an object side to an image side, a first power prism  790 A, a lens barrel  730  containing one or more refractive lens elements, a second power prism  790 B, and an image sensor  760 . 
       FIG. 8  is a flowchart of an example method for capturing images using embodiments of a folded lens system that includes a power prism as illustrated in  FIGS. 3 through 7 , according to some embodiments. As indicated at  2000 , light from an object field is received on a first axis, through an aperture stop, at the object side surface of a power prism. In some embodiments, the power prism may include a glass lens (e.g., a plano-convex lens with positive refractive power) attached to the object side of a prism. As shown in  FIG. 6A , in some embodiments, an aperture stop may be located at the outer edge of the glass lens. As indicated at  2010 , the light received at the object side of the power prism is redirected by the prism through an image side of the prism to a lens stack including one or more refractive lens elements on a second axis. In some embodiments, the power prism may include a glass lens (e.g., a concave lens with negative refractive power) attached to the image side of a prism. As indicated at  2020 , the light received from the power prism is then refracted by the one or more lens elements in the lens stack to a second prism. In some embodiments, the second prism may also be a power prism that includes a glass lens attached to at least one surface of the prism. As indicated at  2030 , the second prism redirects the light to form an image at an image plane at or near the surface of an image sensor or sensor module on a third axis. An image may then be captured by the image sensor or sensor module. 
     In some embodiments, there may be no second prism, for example as illustrated in  FIG. 7B . In these embodiments, the lens stack refracts light to form an image at or near the surface of an image sensor or sensor module on the second axis. 
     In some embodiments, the light may pass through an infrared filter that may for example be located between the lens stack and the image sensor. 
       FIG. 9  is a flowchart of a method for manufacturing a power prism as illustrated in  FIG. 3 , according to some embodiments. As indicated at  2100 , an optical glass wafer is molded to form a plurality of lens shapes on a first surface of the wafer, for example as illustrated in  FIGS. 5A through 5C . As indicated at  2110 , the molded glass wafer is ground and polished from a second surface to produce singulated glass lenses with no flanges, for example as illustrated in  FIGS. 5D and 5E . As indicated at  2120 , the singulated lenses are attached to surfaces of glass prisms using optical glue or optical contact to produce power prisms, for example as illustrated in  FIGS. 5F and 5G . 
     Example Computing Device 
       FIG. 10  illustrates an example computing device, referred to as computer system  2000 , that may include or host embodiments of a camera with a folded lens system that includes at least one power prism as illustrated in  FIGS. 3 through 9 . In addition, computer system  2000  may implement methods for controlling operations of the camera and/or for performing image processing of images captured with the camera. In different embodiments, computer system  2000  may be any of various types of devices, including, but not limited to, a personal computer system, desktop computer, laptop, notebook, tablet or pad device, slate, or netbook computer, mainframe computer system, handheld computer, workstation, network computer, a camera, a set top box, a mobile device, a wireless phone, a smartphone, a consumer device, video game console, handheld video game device, application server, storage device, a television, a video recording device, a peripheral device such as a switch, modem, router, or in general any type of computing or electronic device. 
     In the illustrated embodiment, computer system  2000  includes one or more processors  2010  coupled to a system memory  2020  via an input/output (I/O) interface  2030 . Computer system  2000  further includes a network interface  2040  coupled to I/O interface  2030 , and one or more input/output devices  2050 , such as cursor control device  2060 , keyboard  2070 , and display(s)  2080 . Computer system  2000  may also include one or more cameras  2090 , for example at least one camera that includes a folded lens system with a power prism as described above with respect to  FIGS. 3 through 9 . 
     In various embodiments, computer system  2000  may be a uniprocessor system including one processor  2010 , or a multiprocessor system including several processors  2010  (e.g., two, four, eight, or another suitable number). Processors  2010  may be any suitable processor capable of executing instructions. For example, in various embodiments processors  2010  may be general-purpose or embedded processors implementing any of a variety of instruction set architectures (ISAs), such as the x86, PowerPC, SPARC, or MIPS ISAs, or any other suitable ISA. In multiprocessor systems, each of processors  2010  may commonly, but not necessarily, implement the same ISA. 
     System memory  2020  may be configured to store program instructions  2022  and/or data  2032  accessible by processor  2010 . In various embodiments, system memory  2020  may be implemented using any suitable memory technology, such as static random access memory (SRAM), synchronous dynamic RAM (SDRAM), nonvolatile/Flash-type memory, or any other type of memory. In the illustrated embodiment, program instructions  2022  may be configured to implement various interfaces, methods and/or data for controlling operations of camera  2090  and for capturing and processing images with integrated camera  2090  or other methods or data, for example interfaces and methods for capturing, displaying, processing, and storing images captured with camera  2090 . In some embodiments, program instructions and/or data may be received, sent or stored upon different types of computer-accessible media or on similar media separate from system memory  2020  or computer system  2000 . 
     In one embodiment, I/O interface  2030  may be configured to coordinate I/O traffic between processor  2010 , system memory  2020 , and any peripheral devices in the device, including network interface  2040  or other peripheral interfaces, such as input/output devices  2050 . In some embodiments, I/O interface  2030  may perform any necessary protocol, timing or other data transformations to convert data signals from one component (e.g., system memory  2020 ) into a format suitable for use by another component (e.g., processor  2010 ). In some embodiments, I/O interface  2030  may include support for devices attached through various types of peripheral buses, such as a variant of the Peripheral Component Interconnect (PCI) bus standard or the Universal Serial Bus (USB) standard, for example. In some embodiments, the function of I/O interface  2030  may be split into two or more separate components, such as a north bridge and a south bridge, for example. Also, in some embodiments some or all of the functionality of I/O interface  2030 , such as an interface to system memory  2020 , may be incorporated directly into processor  2010 . 
     Network interface  2040  may be configured to allow data to be exchanged between computer system  2000  and other devices attached to a network  2085  (e.g., carrier or agent devices) or between nodes of computer system  2000 . Network  2085  may in various embodiments include one or more networks including but not limited to Local Area Networks (LANs) (e.g., an Ethernet or corporate network), Wide Area Networks (WANs) (e.g., the Internet), wireless data networks, some other electronic data network, or some combination thereof. In various embodiments, network interface  2040  may support communication via wired or wireless general data networks, such as any suitable type of Ethernet network, for example; via telecommunications/telephony networks such as analog voice networks or digital fiber communications networks; via storage area networks such as Fibre Channel SANs, or via any other suitable type of network and/or protocol. 
     Input/output devices  2050  may, in some embodiments, include one or more display terminals, keyboards, keypads, touchpads, scanning devices, voice or optical recognition devices, or any other devices suitable for entering or accessing data by computer system  2000 . Multiple input/output devices  2050  may be present in computer system  2000  or may be distributed on various nodes of computer system  2000 . In some embodiments, similar input/output devices may be separate from computer system  2000  and may interact with one or more nodes of computer system  2000  through a wired or wireless connection, such as over network interface  2040 . 
     As shown in  FIG. 10 , memory  2020  may include program instructions  2022 , which may be processor-executable to implement any element or action to support integrated camera  2090 , including but not limited to image processing software and interface software for controlling camera  2090 . In some embodiments, images captured by camera  2090  may be stored to memory  2020 . In addition, metadata for images captured by camera  2090  may be stored to memory  2020 . 
     Those skilled in the art will appreciate that computer system  2000  is merely illustrative and is not intended to limit the scope of embodiments. In particular, the computer system and devices may include any combination of hardware or software that can perform the indicated functions, including computers, network devices, Internet appliances, PDAs, wireless phones, pagers, video or still cameras, etc. Computer system  2000  may also be connected to other devices that are not illustrated, or instead may operate as a stand-alone system. In addition, the functionality provided by the illustrated components may in some embodiments be combined in fewer components or distributed in additional components. Similarly, in some embodiments, the functionality of some of the illustrated components may not be provided and/or other additional functionality may be available. 
     Those skilled in the art will also appreciate that, while various items are illustrated as being stored in memory or on storage while being used, these items or portions of them may be transferred between memory and other storage devices for purposes of memory management and data integrity. Alternatively, in other embodiments some or all of the software components may execute in memory on another device and communicate with the illustrated computer system  2000  via inter-computer communication. Some or all of the system components or data structures may also be stored (e.g., as instructions or structured data) on a computer-accessible medium or a portable article to be read by an appropriate drive, various examples of which are described above. In some embodiments, instructions stored on a computer-accessible medium separate from computer system  2000  may be transmitted to computer system  2000  via transmission media or signals such as electrical, electromagnetic, or digital signals, conveyed via a communication medium such as a network and/or a wireless link. Various embodiments may further include receiving, sending or storing instructions and/or data implemented in accordance with the foregoing description upon a computer-accessible medium. Generally speaking, a computer-accessible medium may include a non-transitory, computer-readable storage medium or memory medium such as magnetic or optical media, e.g., disk or DVD/CD-ROM, volatile or non-volatile media such as RAM (e.g. SDRAM, DDR, RDRAM, SRAM, etc.), ROM, etc. In some embodiments, a computer-accessible medium may include transmission media or signals such as electrical, electromagnetic, or digital signals, conveyed via a communication medium such as network and/or a wireless link. 
     The methods described herein may be implemented in software, hardware, or a combination thereof, in different embodiments. In addition, the order of the blocks of the methods may be changed, and various elements may be added, reordered, combined, omitted, modified, etc. Various modifications and changes may be made as would be obvious to a person skilled in the art having the benefit of this disclosure. The various embodiments described herein are meant to be illustrative and not limiting. Many variations, modifications, additions, and improvements are possible. Accordingly, plural instances may be provided for components described herein as a single instance. Boundaries between various components, operations and data stores are somewhat arbitrary, and particular operations are illustrated in the context of specific illustrative configurations. Other allocations of functionality are envisioned and may fall within the scope of claims that follow. Finally, structures and functionality presented as discrete components in the example configurations may be implemented as a combined structure or component. These and other variations, modifications, additions, and improvements may fall within the scope of embodiments as defined in the claims that follow.

Metadata:
Filing Date: 20190826
Publication Date: 20220524
Grant Date: 20220524
Priority Date: 20180831
Inventors: SHIGEMITSU, NORIMICHI
FUJITA, KAZUYA
TANAKA, HIDEKI
HUANG, SHUO WEI
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B5/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B17/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B17/006", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29D11/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B13/007", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B13/0085", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B7/1805", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B7/02", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 69639705