Optical System

Abstract

An optical system is provided that reduces defocusing and degradation of image quality captured by a camera system. [Solution] In an optical system including a substrate, an image sensor on the substrate having an image plane, a lens barrel defining a mechanical axis intersecting the image sensor and the image plane and having a first coefficient of thermal expansion (CTE), a lens mount integrally formed with the lens barrel and bonded to the substrate and having a second CTE, and a lens element defining an optical axis intersecting the image sensor and the image plane, wherein a final magnification-adjusted optical surface of the lens element is spaced along the optical axis from the image plane by a back focal length, at least one of the first and second CTEs limits changes in the back focal length as a result of temperature changes in the optical system to prevent defocusing and degradation of images received by the image sensor.

Description

[Technical Field]

[0001] The present invention is directed to optical systems, and more particularly to optical systems having a lens barrel integrally formed with a lens mount. [Background technology]

[0002] Advanced driver assistance systems ("ADAS") for vehicles are known. One type of vehicular ADAS uses a forward-facing camera system. The camera system is fixed to the vehicle's windshield to provide a forward view in front of the vehicle. Such forward-facing vehicular ADAS devices monitor the operating environment ahead of the vehicle and provide monitored environmental information to other vehicle systems to assist in vehicle operation. For example, a vehicular ADAS may monitor lane departure, assist in keeping the vehicle in its lane, provide lane centering / lane guidance, control operation of high-beam and / or low-beam headlights, detect vehicle presence, provide forward collision warning, perform sign recognition, and / or activate automatic emergency braking in response to pedestrian detection. A vehicular ADAS controller is connected to the output of the camera system and analyzes image output data from the camera.

[0003] A camera system may include multiple lens elements that direct light to an image sensor. The back focal lengths of the lens elements are selected so that the optical system is focused and a clear image is captured by the image sensor. Expansion or contraction of the camera system caused by temperature changes in the camera system can change the selected back focal length, which can result in defocusing and degradation of the image quality captured by the camera system. Summary of the Invention [Problem to be solved by the invention]

[0004] It is an object of the present invention to provide an optical system that reduces defocusing and degradation of image quality captured by a camera system. [Means for solving the problem]

[0005] According to one aspect, an optical system includes a substrate. An image sensor is located on the substrate. The image sensor has an image plane. A lens barrel defines a mechanical axis that intersects the image sensor and the image plane. The lens barrel has a first coefficient of thermal expansion (CTE). A lens mount is integrally formed with the lens barrel. The lens mount is coupled to the substrate. The lens mount has a second CTE. At least one lens element is located on the lens barrel at the mechanical axis and defines an optical axis that intersects the image sensor and the image plane. A final magnified optical surface of the at least one lens element is spaced from the image plane along the optical axis by a back focal length. At least one of the first and second CTEs limits changes in the back focal length as a result of temperature changes in the optical system to prevent defocusing and degradation of an image received by the image sensor.

[0006] According to another aspect, alone or in combination with any other abstract object, the optical system can include a substrate. The image sensor can be on the substrate. The lens barrel can define a mechanical axis that intersects the image sensor and the image plane. The lens mount can be integrally formed with the lens barrel such that the lens barrel and the mount are configured as a single unit. The lens mount can be coupled to the substrate and can couple the lens barrel to the substrate. At least one lens element can be on the lens barrel at the mechanical axis.

[0007] These and other features of the present invention will become apparent to those skilled in the art to which the present invention pertains upon consideration of the following description of the invention which refers to the accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of an optical system made in accordance with one embodiment of the present invention. [Figure 2] 10 is a cross-sectional view of an optical system made in accordance with another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] FIG. 1 illustrates an optical system 10 that can be used in an advanced driver assistance system (“ADAS”) 12 for a vehicle. When used in an ADAS 12, the optical system 10 can be fixed to a window, such as a front window, side window, or rear window of the vehicle. The ADAS 12 can monitor the vehicle's operating environment and provide monitored environmental information to other vehicle systems to assist in vehicle operation. For example, the ADAS 12 can monitor lane departure, assist in keeping the vehicle in its lane, provide lane centering / lane guidance, control operation of high and / or low beam headlights, detect vehicle presence, provide forward collision warning, perform sign recognition, and / or activate automatic emergency braking in response to pedestrian detection. An ADAS controller can be connected to the output of the optical system 10 and can analyze image output data from the optical system.

[0010] As shown in FIG. 1 , optical system 10 includes a substrate 14. Substrate 14 may be a printed circuit board (“PCB”) and is therefore referred to herein as a PCB. An image sensor 16 resides on PCB 14. Image sensor 16 can be coupled to PCB 14 in any desired manner, such as by soldering. Image sensor 16 defines an image plane 18 that is spaced apart from PCB 14 by an image plane distance 20. One or more materials forming image sensor 16 are selected such that the image sensor has a sensor coefficient of thermal expansion (“CTE”) that determines how a length 22 of the image sensor, measured along a mechanical axis 24, changes, i.e., expands or contracts along the mechanical axis as the temperature of optical system 10 changes. A change in length 22 of image sensor 16 causes a corresponding increase or decrease in image plane distance 20.

[0011] The lens barrel 26 is integrally formed with the lens mount 28 such that the lens barrel and the mount are configured as a single unit. The lens mount 28 and the lens barrel 26 are integrally formed by a two-step injection molding process or an insert molding process. Thus, the integrally formed lens barrel 26 and lens mount 28 are not joined to each other by fasteners, adhesive bonding, or soldering. The lens mount 28 couples the lens barrel 26 to the PCB 14. The lens barrel 26 defines a mechanical axis 24. The mechanical axis 24 intersects the image sensor 16 and the image plane 18.

[0012] The lens barrel 26 has integrally formed first and second barrel portions 30, 32. The first and second barrel portions 30, 32 may be integrally formed by an injection molding process, an overmolding process, a two-stage injection molding process, or an insert molding process. The first and second barrel portions 30, 32 may be formed from one or more of aluminum, brass, and a polymer, for example. One or more materials forming the first barrel portion 30 are selected to have a first barrel CTE that determines how the length 34 of the first barrel portion, measured along the mechanical axis 24, changes, i.e., expands or contracts along the mechanical axis as the temperature of the optical system 10 changes. One or more materials forming the second barrel portion 32 are selected to have a second barrel CTE that determines how the length 36 of the second barrel portion, measured along the mechanical axis 24, changes, i.e., expands or contracts along the mechanical axis as the temperature of the optical system 10 changes.

[0013] As shown in the exemplary configuration of Figure 1, the first and second barrel sections 30, 32 can be formed of the same material or materials such that the first and second barrel CTEs are the same. Alternatively, as shown in the exemplary configuration of Figure 2, the first and second barrel sections 30, 32 can be different such that the first barrel CTE is different from the second barrel CTE.

[0014] As shown in FIG. 1 , the first barrel portion 30 includes a substantially cylindrical flange 38 and a substantially cylindrical portion 40 extending from the flange in a first direction FD along the mechanical axis 24 away from the PCB 14. The first barrel portion 30 defines a first barrel opening 42 extending through the first barrel portion along the mechanical axis 24. The second barrel portion 32 is substantially cylindrical and extends in a second direction SD from the flange 38 toward the PCB 14 opposite the first direction FD. The second barrel portion 32 defines a second barrel opening 44 extending through the second barrel portion along the mechanical axis 24. The first and second barrel openings 42, 44 together form a lens barrel opening 46 extending entirely through the lens barrel 26 along the mechanical axis 24.

[0015] The lens mount 28 is substantially cylindrical and extends from the flange 38 in the second direction SD along the mechanical axis 24. The lens mount 28 is directly bonded to the PCB 14 by a layer of adhesive 54 between the lens mount and the PCB. The lens mount 28 defines a mounting opening 48 through which the second barrel portion 32 extends. The lens mount 28 and the flange 38 engage each other at a mating plane 50 that extends transversely to the mechanical axis 24.

[0016] Lens mount 28 may be substantially cylindrical. Alternatively, lens mount 28 can be configured such that the interface between the lens mount and lens barrel 26 is substantially cylindrical, while the interface between the lens mount and PCB 14 is square or rectangular. Thus, lens mount 28 has a substantially cylindrical portion for connecting with lens barrel 26 and a substantially square or rectangular portion for connecting with PCB 14.

[0017] Lens mount 28 may be formed from one or more of aluminum, brass, and polymer, for example. The material or materials forming lens mount 28 are selected so that the lens mount has a mount CTE that defines how the lens mount length 52, measured along mechanical axis 24, changes, i.e., expands or contracts along the mechanical axis as the temperature of optical system 10 changes.

[0018] The material or materials forming adhesive layer 54 are selected so that the adhesive layer has an adhesive CTE that determines how the adhesive layer's length 56, measured along mechanical axis 24, changes, i.e., expands or contracts along the mechanical axis, as the temperature of optical system 10 changes. Although lens mount 28 is shown and described as being coupled to PCB 14 by adhesive layer 54, the lens mount can be coupled to the PCB in any other desired manner, such as by soldering or one or more fasteners.

[0019] At least one lens element 58, 60, 62, 64, 66 resides in the lens barrel 26 at the mechanical axis 24 and is used to direct light to the image sensor 16. As shown in the exemplary configuration of FIG. 1 , the first barrel section 30 has multiple lens elements 58, 60, 62, 64 at the first barrel opening 42 at the mechanical axis 24. The second barrel section 32 has one lens element 66 at the second barrel opening 44 at the mechanical axis 24. Each lens element 58, 60, 62, 64, 66 may be formed from one or more of glass, polymer, polycarbonate, acrylic glass, and cyclic olefin-based copolymer. The material or materials forming each lens element 58, 60, 62, 64, 66 are selected to have a lens CTE that defines how the length of each lens element, measured along the mechanical axis 24, changes, i.e., whether it expands or contracts along the mechanical axis as the temperature of the optical system 10 changes.

[0020] Lens elements 58, 60, 62, 64, and 66 define an optical axis 25 that intersects image sensor 16 and image plane 18. As shown in Figure 1, axes 24 and 25 are coaxial. Alternatively, axes 24 and 25 may be substantially coaxial. Substantially coaxial axes 24 and 25 may be offset from one another by a small degree.

[0021] Lens element 66 defines a final powered optical surface 68 of lens elements 58, 60, 62, 64, and 66. Final powered optical surface 68 is the non-planar optical surface of lens elements 58, 60, 62, 64, and 66 that is closest to image plane 18. The distance between image plane 18 and an intersection point 70 at powered optical surface 68 where optical axis 25 intersects the powered optical surface is referred to as a back focal length 72. Back focal length 72 is selected so that optical system 10 is focused and a sharp image is captured by image sensor 16. The selected back focal length 72 can be determined based on a temperature of optical system 10 of 25° C.

[0022] The optical system 10 may further include one or more spacer elements 74, 76, 78 and / or one or more retainers 80, 82. The spacer elements 74, 76, 78 and the retainers 80, 82 hold the lens elements 58, 60, 62, 64, 66 in the lens barrel 26. As shown in FIG. 1 , there are multiple spacer elements 74, 76, 78 in the lens barrel 26. Each spacer element 74, 76, 78 engages two adjacent lens elements 58, 60, 62, 64, 66 or engages a lens element with an adjacent shoulder 84 on the lens barrel 26. The shoulder 84 extends radially toward the mechanical axis 24 and into the first barrel opening 42. The spacer elements 74, 76, 78 may be formed from one or more of aluminum, brass, and polymer. The material or materials forming the spacer elements 74, 76, 78 are selected so that each spacer element has a spacer CTE that defines how the length of each spacer element, measured along the mechanical axis 24, changes, i.e., whether it expands or contracts along the mechanical axis as the temperature of the optical system 10 changes.

[0023] 1 , the first retainer 80 can be coupled, for example, threaded, to the first barrel portion 30. The first retainer 80 helps prevent the lens elements 58, 60, 62 and the spacer elements 74, 76 between the shoulder portion 84 and the first retainer from moving from their predetermined positions in the lens barrel 26. The second retainer 82 can be coupled, for example, threaded, to the second barrel portion 32. The second retainer 82 helps prevent the lens elements 64, 66 and the spacer element 78 between the shoulder portion 84 and the second retainer from moving from their predetermined positions in the lens barrel 26. The first and second retainers 80, 82 can be formed from one or more of metal, aluminum, brass, and polymer.

[0024] A filter lens 86 may be coupled to the second retainer 82. The filter lens 86 extends along the mechanical axis 24. The filter lens 86 may help protect the image sensor 16 and the lens elements 58, 60, 62, 64, and 66. The filter lens 86 may also change the characteristics of light passing through the lens elements 58, 60, 62, 64, and 66 to the image sensor 16. The filter lens 86 may be formed from one or more of a polymer, polycarbonate, polyphenylene sulfide, acrylic glass, and a cyclic olefin copolymer.

[0025] A change in the temperature of the optical system 10 from 25° C. may change the selected back focal length 72 of the optical system. A change in the length 36 of the second barrel portion 32 as a result of a change in the temperature of the optical system 10 from 25° C. may increase or decrease the distance 88 between the intersection point 70 and the coupling plane 50 (referred to herein as the coupling plane distance 88). The second barrel CTE causes the length 36 of the second barrel portion 32 to expand in the second direction SD toward the PCB 14 when the temperature of the optical system 10 increases. The second barrel portion 32 expands in the second direction SD because the flange 38 of the first barrel portion 30 prevents the second barrel portion 32 from expanding in the first direction FD. The expanding second barrel portion 32 urges the intersection point 70 of the last optical surface 68 in the second direction SD, away from the coupling plane 50, to increase the coupling plane distance 88. The increase in the coupling plane distance 88 may decrease the back focal length 72. Conversely, the second barrel CTE causes the length 36 of the second barrel section 32 to contract in the first direction FD, away from the PCB 14, when the temperature of the optical system 10 decreases. The contracting second barrel section 32 urges the intersection point 70 in the second direction FD, toward the coupling plane 50, to decrease the coupling plane distance 88. The decrease in coupling plane distance 88 may increase the back focal length 72.

[0026] The mount CTE causes the length 52 of the lens mount 28 to expand in a first direction FD, away from the PCB 14, when the temperature of the optical system 10 increases. The expanding lens mount 28 urges the lens barrel 26 and the coupling plane 50 in the first direction FD, away from the PCB 14. The expanding lens mount 28 also urges the lens elements 58, 60, 62, 64, 66, and the intersection point 70 in the first direction FD, away from the image plane 18. Conversely, the mount CTE causes the length 52 of the lens mount 28 to contract in a second direction SD, toward the PCB 14, when the temperature of the optical system 10 decreases. The contracting lens mount 28 urges the lens barrel 26 and the coupling plane 50 in the second direction SD, toward the PCB 14. The contracting lens mount 28 also urges the lens elements 58, 60, 62, 64, 66, and the intersection point 70 in the second direction SD, toward the image plane 18.

[0027] The adhesive CTE causes the length 56 of the adhesive layer 54 to expand in a first direction FD away from the PCB 14 when the temperature of the optical system 10 increases. The expanding adhesive layer 54 urges the lens mount 28 and the lens barrel 26 in the first direction FD away from the PCB 14. The expanding adhesive layer 54 also urges the lens elements 58, 60, 62, 64, 66 and the intersection 70 in the first direction FD away from the image plane 18. Conversely, the adhesive CTE causes the length 56 of the adhesive layer 54 to contract in a second direction SD toward the PCB 14 when the temperature of the optical system 10 decreases. The shrinking adhesive layer 54 urges the lens mount 28 and the lens barrel 26 in the second direction SD toward the PCB 14. The shrinking adhesive layer 54 also urges the lens elements 58, 60, 62, 64, 66 and the intersection 70 in the second direction SD toward the image plane 18.

[0028] The sensor CTE causes the length 22 of the image sensor 16 to expand in a first direction FD, away from the PCB 14, when the temperature of the optical system 10 increases. The expanding image sensor 16 urges the image plane 18 in the first direction FD, away from the PCB 14, toward the intersection 70. Thus, the expanding image sensor 16 may increase the image plane distance 20. Conversely, the sensor CTE causes the length 22 of the image sensor 16 to contract in a second direction SD, toward the PCB 14, when the temperature of the optical system 10 decreases. The contracting image sensor 16 urges the image plane 18 in the second direction SD, away from the PCB 14, toward the intersection 70. Thus, the contracting image sensor 16 may decrease the image plane distance 20.

[0029] Another factor affecting the selected back focal length 72 is the summation effect of temperature on the lens elements ("summation effect"). The summation effect is a predetermined value that reflects how various factors drive the intersection point 70 toward or away from the image plane 18. The summation effect may include changes in the refractive index of the lens elements 58, 60, 62, 64, and 66 as a result of changes in the temperature of the optical system 10. The change in the refractive index of the lens elements 58, 60, 62, 64, and 66 may be a major factor that drives the selected back focal length 72 to change when the temperature in the optical system 10 changes from 25°C. The summation effect may include changes in the length of the lens elements 58, 60, 62, 64, and 66 as a result of changes in the temperature of the optical system 10. The summation effect may also include how the arc of the lens elements 58, 60, 62, 64, and 66 changes in response to temperature changes. The change in length of the spacer elements 74, 76, 78 may also urge the lens elements 58, 60, 62, 64, 66 towards or away from the image plane 18. Thus, the total effect may include the change in length of the spacer elements 74, 76, 78.

[0030] Therefore, the selected back focal length 72 can be prompted to change based on how a change in temperature of the optical system 10 from 25° C. affects the second barrel section 32, the lens mount 28, the adhesive layer 54, the image sensor 16, and the lens elements 58, 60, 62, 64, and 66. The following equation can be used to ensure that the selected back focal length 72 is limited or prevented to prevent defocus and degradation of the image received by the image sensor 16. ΔBFL=SE+ΔCPD-ΔL LM -ΔL LOA +ΔIPD where ΔBFL is the change in the selected back focal length 72, SE is the summation effect, ΔCPD is the change in the coupling plane distance 88, and ΔL LM is the change in length 52 of the lens mount 28, and ΔL LOA is the change in length 56 of the adhesive layer 54 and ΔIPD is the change in image plane distance 20 .

[0031] The materials and CTEs of one or more of the second barrel section 32, lens mount 28, adhesive layer 54, image sensor 16, lens elements 58, 60, 62, 64, 66, and spacer elements 74, 76, 78 can be selected so that the change in the selected back focal length ΔBFL as a result of a change in temperature of the optical system 10 is zero or near zero. Depending on the design constraints of the optical system, the second barrel section 32 and lens mount 28 can provide maximum flexibility in the materials and CTEs selected. In one configuration, the materials forming the second barrel section 32 and lens mount 28 can be selected so that the second barrel CTE and mount CTE are the same to prevent or minimize the change in the selected back focal length ΔBFL. Alternatively, the materials forming the second barrel section 32 and lens mount 28 can be selected so that the second barrel CTE and mount CTE are different to prevent or minimize the change in the selected back focal length ΔBFL.

[0032] Even though the second barrel section 32 and the lens mount 28 are integrally formed together, the second barrel CTE and the mount CTE can be made different from one another by using two different substrates to form the second barrel section and the lens mount. In one exemplary configuration, the substrate of the second barrel section 32 may be a polymer such as polyphenylene sulfide (“PPS”), while the substrate of the lens mount 28 is aluminum. The PPS forming the second barrel section 32 may be “unfilled.” Unfilled PPS does not contain significant amounts of filler. The CTE of unfilled PPS is typically greater than the CTE of aluminum. Therefore, in this exemplary configuration, the second barrel section 32 has a different CTE than the lens mount 28.

[0033] Alternatively, the second barrel CTE and the mount CTE can be made different even if the second barrel section 32 and the lens mount 28 include the same base material. In one exemplary configuration, the base material of both the second barrel section 32 and the lens mount 28 may be PPS. However, the second barrel section 32 may include approximately 45-70% PPS and approximately 30-55% filler, such as glass fiber, glass beads, and / or mica. The lens mount 28 may include approximately 35-44% PPS and approximately 56-65% filler. Due to the filler used in the second barrel section 32 and the lens mount 28, the second barrel CTE and the mount CTE are typically lower than if the second barrel section and the lens mount did not include filler. Because the second barrel section 32 includes a lower percentage of filler than the lens mount 28, the second barrel CTE is greater than the mount CTE. Thus, even if both the second barrel section 32 and the lens mount 28 comprise the same base material, the second barrel CTE and the mount CTE can be made different from one another by varying the amount of filler contained in the second barrel section and the lens mount, respectively. The second barrel CTE and the mount CTE can also be made different by varying the type of filler contained in the second barrel section 32 and the lens mount 28, when the second barrel section 32 and the lens mount 28 have the same base material.

[0034] The materials and CTE of one or more features of optical system 10, such as second barrel section 32 and / or lens mount 28, can also be selected so that the change in selected back focal length ΔBFL as a result of lowering the temperature of optical system 10 from 25° C. to a given power is approximately the same as the change in selected back focal length as a result of raising the temperature of the optical system from 25° C. to a given power. For example, the change in selected back focal length ΔBFL when optical system 10 is cooled from 25° C. to −40° C. can be approximately the same as the change in selected back focal length when the optical system is heated from 25° C. to 105° C.

[0035] The length of one or more of the lens mount 28, second barrel portion 32, and adhesive layer 54 may also be selected so that the change in the selected back focal length ΔBFL as a result of a change in temperature of the optical system 10 from 25° C. is zero or near zero. LM is one component in the equation to help ensure that a change in the selected back focal length, ΔBFL, is limited or prevented. As the temperature of optical system 10 changes from 25°C, length 52 of lens mount 28 changes by an amount proportional to the length of the lens mount at 25°C and the temperature change. Therefore, in selecting length 52 of lens mount 28 at 25°C, ΔL should be adjusted so that the change in the selected back focal length, ΔBFL, as a result of a change in the temperature of optical system 10 from 25°C is zero or nearly zero. LM The ingredients can be adjusted.

[0036] The change in coupling plane distance ΔCPD is another component in the equation to help ensure that the change in the selected back focal length ΔBFL is limited or prevented. As the temperature of optical system 10 changes from 25°C, coupling plane distance 88 changes by an amount proportional to the length of the coupling plane distance at 25°C and the temperature change. Thus, in selecting the length of the coupling plane distance at 25°C, it is possible to adjust the ΔCPD component so that the change in the selected back focal length ΔBFL as a result of a change in the temperature of optical system 10 from 25°C is zero or near zero.

[0037] If desired, the coupling plane distance 88 at 25° C. can be increased from that shown in FIG. 1 by moving the lens element 66 and / or the intersection point 70 in the second direction SD relative to the coupling plane 50. To accommodate this increase in the coupling plane distance 88, the length 36 that the second barrel section 32 extends from the flange 38 in the second direction SD when the temperature of the optical system 10 is 25° C. can be increased from that shown in FIG. 1. Conversely, the coupling plane distance 88 at 25° C. can be decreased from that shown in FIG. 1 by moving the lens element 66 and / or the intersection point 70 in the first direction FD relative to the coupling plane 50. To accommodate this decrease in the coupling plane distance 88, the length 36 that the second barrel section 32 extends from the flange 38 in the second direction SD when the temperature of the optical system 10 is 25° C. can be decreased from that shown in FIG.

[0038] The coupling plane distance 88 can be selected by selecting the position of the flange 38 along the mechanical axis 24 when the temperature of the optical system 10 is 25° C. For example, the coupling plane distance 88 in FIG. 1 can be increased by moving the flange 38 in a first direction FD along the mechanical axis 24 from the position of the flange shown in FIG. 1 while maintaining the intersection point 70 at a position along the optical axis 25 of the lens barrel 18 shown in FIG. 1. Because the first barrel portion includes a flange and a portion 40 extending from the flange in a first direction FD, moving the flange 38 in the first direction FD can shorten the length 34 of the first barrel portion 30. Because the second barrel portion includes a lens barrel 26 extending from the flange 38 in a second direction SD, moving the flange in the first direction FD can lengthen the length 36 of the second barrel portion 32. As another example, coupling plane distance 88 in Figure 1 can be decreased by moving flange 38 in second direction SD along mechanical axis 24 from the position of the flange shown in Figure 1 while maintaining intersection point 70 at a position along optical axis 25 of lens barrel 18 shown in Figure 1. By moving flange 38 in second direction SD, length 34 of first barrel portion 30 can be increased and length 36 of second barrel portion 32 can be decreased.

[0039] Change in length of lens attachment ΔL LOA is also a component in the equation to help ensure that a change in the selected back focal length, ΔBFL, is limited or prevented. As the temperature of optical system 10 changes from 25°C, length 56 of adhesive layer 54 changes by an amount proportional to the length of the adhesive layer at 25°C and the temperature change. Thus, in selecting length 56 of adhesive layer 54 at 25°C, ΔL should be adjusted so that the change in the selected back focal length, ΔBFL, as a result of a change in the temperature of optical system 10 from 25°C is zero or nearly zero. LOA The ingredients can be adjusted.

[0040] From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of those skilled in the art are intended to be covered by the appended claims. The present invention may also include the following aspects: 1. A substrate; an image sensor in a substrate having an image plane; a lens barrel defining a mechanical axis that intersects the image sensor and the image plane, the lens barrel having a first coefficient of thermal expansion (CTE); a lens mount integrally formed with the lens barrel and coupled to the substrate, the lens mount having a second CTE; at least one lens element in a lens barrel at a mechanical axis and defining an optical axis intersecting the image sensor and an image plane, the at least one lens element having a last powered optical surface spaced along the optical axis from the image plane by a back focal length; It contains 1. An optical system, wherein at least one of the first and second CTEs limits a change in back focal length as a result of a change in temperature of the optical system to prevent defocusing and degradation of an image received by the image sensor. 2. The optical system described in 1. above, characterized in that the lens barrel has first and second integrally formed barrel portions, the first barrel portion including a flange that engages with the lens mount, and the second barrel portion extending from the flange toward the substrate and into a mounting opening in the lens mount. 3. The optical system described in 2 above, wherein the lens mount and flange engage each other at a coupling plane extending transversely to the mechanical axis, and wherein a change in temperature of the optical system causes a change in the length of the second barrel portion measured along the mechanical axis, and correspondingly, the change in length of the second barrel portion urges the final magnification-adjusted optical surface along the optical axis toward or away from the coupling plane. 4. The optical system described in claim 3, wherein the second barrel section has at least one lens element therein, the at least one lens element in the second barrel section having a final power-adjusted optical surface, and wherein an increase in the length of the second barrel section as a result of an increase in temperature of the optical system urges the final power-adjusted optical surface away from the coupling plane along the optical axis, and wherein a decrease in the length of the second barrel section as a result of an increase in temperature of the optical system urges the final power-adjusted optical surface along the optical axis toward the coupling plane. 5. The optical system of claim 2, wherein each of the first and second barrel portions has at least one lens element therein positioned on the mechanical axis. 6. The optical system of claim 2, wherein the second barrel section has a first CTE and the first barrel section has a CTE different from the first CTE. 7. The optical system according to claim 1, wherein the first and second CTEs are the same. 8. The optical system according to claim 1, wherein the first and second CTEs are different from each other. 9. The optical system described in claim 1, characterized in that a change in temperature of the optical system increases or decreases the length of the lens mount measured along the mechanical axis, with an increase in the length of the lens mount urging the last magnified optical surface away from the image plane and a decrease in the length of the lens mount urging the last magnified optical surface towards the image plane. 10. The optical system described in 1 above, further comprising a layer of adhesive between the lens mount and the substrate, bonding the lens mount to the substrate, the adhesive layer having an adhesive CTE, and wherein a change in temperature of the optical system increases or decreases the length of the adhesive layer measured along the mechanical axis, an increase in the length of the adhesive layer urging the last magnified optical surface away from the image plane and a decrease in the length of the adhesive layer urging the last magnified optical surface towards the image plane. 11. The optical system described in claim 1, wherein the image sensor has a third CTE, and wherein a change in temperature of the optical system causes the length of the image sensor measured along the mechanical axis to increase or decrease, with an increase in the length of the image sensor urging the image plane toward the last magnified optical surface and a decrease in the length of the image sensor urging the image plane away from the last magnified optical surface. 12. The optical system of claim 1, wherein the length of the lens mount, measured along the mechanical axis, is selected to further limit changes in the back focal length as a result of temperature changes in the optical system. 13. The optical system described in claim 1, wherein the lens mount and lens barrel engage each other at a coupling plane extending transversely to the mechanical axis, the optical axis intersects the last power-adjusted optical surface at an intersection point, and the distance between the coupling plane and the intersection point, measured along the mechanical or optical axis, is selected to further limit changes in back focal length as a result of temperature changes in the optical system. 14. The optical system described in claim 1, wherein a change in temperature of the optical system causes a change in the length of at least one lens element measured along the optical axis, an arc of at least one lens element, and an index of refraction of at least one lens element, and the change in the length, arc, and index of refraction of the at least one lens element causes the final magnified optical surface to move toward or away from the image plane. 15. The optical system described in claim 14, further comprising at least one spacer element in the lens barrel to hold the at least one lens element in the lens barrel, wherein a change in temperature of the optical system causes a change in length of the at least one spacer element measured along the optical axis, and the change in length of the at least one spacer element urges the final magnification-adjusted optical surface along the optical axis toward or away from the image plane. 16. A driver assistance system including the optical system described in 1 above. 17. A substrate; an image sensor on the substrate; a lens barrel defining a mechanical axis that intersects the image sensor; a lens mount integrally formed with the lens barrel such that the lens barrel and the mount are configured as a unitary member and coupled to the substrate to couple the lens barrel to the substrate; at least one lens element located in a lens barrel at a mechanical axis; An optical system comprising: 18. The optical system described in claim 17, characterized in that the lens barrel has first and second integrally formed barrel portions, the first barrel portion including a flange that engages with the lens mount, and the second barrel portion extending from the flange toward the substrate and into a mounting opening in the lens mount. 19. The optical system described in paragraph 17 above, wherein the lens mount and flange engage each other at a coupling plane extending transversely to the mechanical axis, the optical axis defined by at least one lens element intersects the last power-adjusted optical surface of at least one lens element at an intersection point, and the distance between the coupling plane and the intersection point, measured along the mechanical or optical axis, is selected to further limit changes in the back focal length as a result of temperature changes in the optical system. 20. The optical system described in claim 17, wherein the image sensor has an image plane, the last optical surface of the at least one lens element is spaced from the image plane by a back focal length along an optical axis defined by the at least one lens element, the lens barrel has a first coefficient of thermal expansion (CTE), and the lens mount has a second CTE, and at least one of the first and second CTEs limits changes in the back focal length as a result of temperature changes in the optical system to prevent defocusing and degradation of images received by the image sensor. 21. The optical system of claim 17, wherein the length of the lens mount, measured along the mechanical axis, is selected to further limit changes in back focal length as a result of temperature changes in the optical system.

Claims

1. A substrate; an image sensor in a substrate having an image plane; a lens barrel defining a mechanical axis that intersects the image sensor and the image plane and having a first coefficient of thermal expansion (CTE); a lens mount integrally formed with the lens barrel and coupled to the substrate, the lens mount having a second CTE; at least one lens element in a lens barrel at a mechanical axis and defining an optical axis intersecting the image sensor and an image plane, the at least one lens element having a last powered optical surface spaced along the optical axis from the image plane by a back focal length; It contains 1. An optical system comprising: at least one of the first and second CTEs limiting a change in back focal length as a result of temperature changes of the optical system to prevent defocusing and degradation of an image received by an image sensor; a lens barrel having first and second integrally formed barrel portions aligned with one another along a mechanical axis, the first barrel portion including a flange for engaging a lens mount, the second barrel portion extending from the flange toward the substrate to a mounting opening in the lens mount; and the second barrel portion having a first CTE and the first barrel portion having a CTE different from the first CTE.

2. 10. The optical system of claim 1, wherein the lens mount and flange engage each other at a coupling plane extending transverse to the mechanical axis, and wherein a temperature change in the optical system causes a change in the length of the second barrel portion measured along the mechanical axis, such that the change in length of the second barrel portion correspondingly urges the final power-adjusted optical surface along the optical axis toward or away from the coupling plane.

3. 3. The optical system of claim 2, wherein the second barrel section has at least one lens element therein, the at least one lens element in the second barrel section having a final power-adjusted optical surface, and wherein an increase in the length of the second barrel section as a result of an increase in temperature of the optical system urges the final power-adjusted optical surface away from the coupling plane along the optical axis, and wherein a decrease in the length of the second barrel section as a result of an increase in temperature of the optical system urges the final power-adjusted optical surface along the optical axis toward the coupling plane.

4. 2. The optical system of claim 1, wherein each of the first and second barrel portions has at least one lens element therein positioned on the mechanical axis.

5. 2. The optical system of claim 1, wherein the first and second CTEs are the same.

6. 10. The optical system of claim 1, wherein the first and second CTEs are different from one another.

7. 10. The optical system of claim 1, wherein a temperature change in the optical system causes the length of the lens mount, measured along the mechanical axis, to increase or decrease, with an increase in the length of the lens mount urging the last magnified optical surface away from the image plane and a decrease in the length of the lens mount urging the last magnified optical surface towards the image plane.

8. 10. The optical system of claim 1, further comprising a layer of adhesive between the lens mount and the substrate, bonding the lens mount to the substrate, the layer of adhesive having an adhesive CTE, wherein a change in temperature of the optical system causes a length of the adhesive layer measured along the mechanical axis to increase or decrease, an increase in the length of the adhesive layer urging the last magnified optical surface away from the image plane and a decrease in the length of the adhesive layer urging the last magnified optical surface towards the image plane.

9. 2. The optical system of claim 1, wherein the image sensor has a third CTE, and wherein a change in temperature of the optical system causes a length of the image sensor measured along the mechanical axis to increase or decrease, with an increase in the length of the image sensor urging the image plane toward the last magnified optical surface and a decrease in the length of the image sensor urging the image plane away from the last magnified optical surface.

10. 10. The optical system of claim 1, wherein the length of the lens mount, measured along the mechanical axis, is selected to further limit changes in back focal length as a result of temperature changes in the optical system.

11. 2. The optical system of claim 1, wherein the lens mount and lens barrel engage each other at a coupling plane extending transversely to the mechanical axis, the optical axis intersecting the last power-adjusted optical surface at an intersection point, and the distance between the coupling plane and the intersection point, measured along the mechanical or optical axis, is selected to further limit changes in back focal length as a result of temperature changes in the optical system.

12. 10. The optical system of claim 1, wherein a temperature change in the optical system causes a change in the length of at least one lens element measured along the optical axis, an arc of at least one lens element, and an index of refraction of at least one lens element, and the change in the length, arc, and index of refraction of the at least one lens element urges the final powered optical surface toward or away from the image plane.

13. 13. The optical system of claim 12, further comprising at least one spacer element in the lens barrel to hold the at least one lens element in the lens barrel, wherein a temperature change in the optical system causes a change in length of the at least one spacer element measured along the optical axis, and the change in length of the at least one spacer element urges the final magnified optical surface along the optical axis toward or away from the image plane.

14. A driver assistance system comprising the optical system of claim 1.

15. A substrate; an image sensor on the substrate; a lens barrel defining a mechanical axis that intersects the image sensor; a lens mount integrally formed with the lens barrel such that the lens barrel and the mount are configured as a unitary member and coupled to the substrate to couple the lens barrel to the substrate; at least one lens element in a lens barrel at a mechanical axis; the lens barrel having first and second integrally formed barrel portions aligned with one another along a mechanical axis, the first barrel portion including a flange that engages a lens mount, the second barrel portion extending from the flange toward the substrate to a mounting opening in the lens mount, and the second barrel portion having a first CTE and the first barrel portion having a CTE different from the first CTE.

16. 16. The optical system of claim 15, wherein the lens mount and flange engage each other at a coupling plane extending transversely to the mechanical axis, an optical axis defined by at least one lens element intersects a last power-adjusted optical surface of the at least one lens element at an intersection point, and a distance between the coupling plane and the intersection point, measured along the mechanical or optical axis, is selected to further limit changes in back focal length as a result of temperature changes in the optical system.

17. 16. The optical system of claim 15, wherein the image sensor has an image plane, a last optical surface of the at least one lens element is spaced from the image plane by a back focal length along an optical axis defined by the at least one lens element, the lens barrel having a first coefficient of thermal expansion (CTE), and the lens mount having a second CTE, wherein at least one of the first and second CTEs limits changes in the back focal length as a result of changes in temperature of the optical system to prevent defocusing and degradation of images received by the image sensor.

18. 16. The optical system of claim 15, wherein the length of the lens mount, measured along the mechanical axis, is selected to further limit changes in back focal length as a result of temperature changes in the optical system.

Images