Multi-element wide field lens for chip cube camera for wafer assembly

Abstract

A chip-level camera and a method of manufacturing a chip cube camera are provided. The chip-level camera includes an image sensor; a concave L1 lens element on an inner surface of a first substrate; a convex L2 lens element on a first surface of a second substrate; an aperture stop on a second surface of the second substrate or on a first surface of a third substrate, the aperture stop being between the second substrate and the third substrate; a convex L3 lens element on a second surface of the third substrate spaced apart from the image sensor; a first spacer maintaining a predetermined distance between the first substrate and the second substrate; and a second spacer maintaining a predetermined distance between the second substrate and the image sensor. In embodiments, the lens element L1 has a concave aspheric radius R1, the lens L2 has a convex aspheric radius R2, such that 1.3 < ABS(R2 / R1) < 2.2 and / or the lens L3 has a convex aspheric radius R3, where 1.1 < ABS(R3 / R1) < 2.4.

Description

Technical Field

[0001] The present invention relates to the field of image sensors, and in particular to a chip-level camera and a method for manufacturing a chip cube camera. Background Art

[0002] Micro chip cube cameras can be produced using various techniques including wafer-level assembly. These miniature cameras have a wide range of applications in endoscopes and borescopes, mobile phones and tablet computers, security cameras, vehicles, and other applications where a small, unobtrusive camera is desired. This diversity of applications leads to a wide range of lens requirements. For certain applications, a lens system with a wide field of view (FOV), compact size and good optical performance is required. Summary of the Invention

[0003] The chip-level camera, designated as A, comprises an image sensor; a concave L1 lens element on an inner surface of a first substrate; a convex L2 lens element on a first surface of a second substrate; an aperture stop on a second surface of the second substrate or on a first surface of a third substrate, the aperture stop being located between the second substrate and the third substrate; a convex L3 lens element on a second surface of the third substrate spaced apart from the image sensor; a first spacer configured to maintain the first substrate and the second substrate at a predetermined distance; and a second spacer configured to maintain the second substrate and the image sensor at a predetermined distance. In an embodiment, the lens element L1 has a concave aspheric radius R1, the lens L2 has a convex aspheric radius R2 such that 1.3 < ABS(R2 / R1) < 2.2, and the lens L3 has a convex aspheric radius R3, wherein 1.1 < ABS(R3 / R1) < 2.4.

[0004] In one aspect, a chip-level camera comprises: an image sensor integrated circuit having a photoelectric sensor array; a concave L1 lens element formed on an inner surface of a first substrate; a convex L2 lens element formed on a first surface of a second substrate; an aperture stop formed on a second surface of the second substrate or on a first surface of a third substrate, the aperture stop being located between the second substrate and the third substrate; a convex L3 lens element formed on a second surface of the third substrate spaced apart from the image sensor integrated circuit; a first spacer configured to maintain the first substrate and the second substrate at a predetermined distance; and a second spacer configured to maintain the second substrate and the image sensor integrated circuit at a predetermined distance; wherein the lens element L1 has a concave aspheric radius R1, the lens L2 has a convex aspheric radius R2, such that 1.3 is less than an absolute value of R2 divided by R1, and the absolute value of R2 divided by R1 is less than 2.2.

[0005] In some embodiments, the lens L3 has a convex aspheric surface with a radius R3, wherein 1.1 is less than an absolute value of R3 divided by R1, and the absolute value of R3 divided by R1 is less than 2.4.

[0006] In some embodiments, lenses L1, L2, and L3 are formed of a reflowable moldable polymer with a refractive index between 1.48 and 1.66 and an Abbe number between 19 and 60.

[0007] In some embodiments, the first spacer and the second spacer are respectively formed as spacer arms for the L1 lens and the L3 lens.

[0008] In some embodiments, the first spacer and the second spacer are respectively formed as spacer arms for an L2 lens and an L3 lens.

[0009] In some embodiments, the first spacer and the second spacer are formed as separate spacer wafers.

[0010] In another aspect, a method of manufacturing a chip cube camera includes: forming an array of first lenses of a reflowable molding material having a first radius (R1) on a first substrate, wherein the refractive index of the reflowable molding material is between 1.48 and 1.66; forming an array of second lenses of a reflowable molding material having a second radius (R2) on a second substrate; forming an array of third lenses of a reflowable molding material having a third radius (R3); forming an aperture stop on the second or third substrate; manufacturing a wafer of an image sensor integrated circuit; sequentially stacking the substrate having lenses and the wafer of the image sensor integrated circuit such that L1 precedes L2, L2 precedes L3 and L3 precedes the image sensor integrated circuit; bonding the lenses and the wafer of the image sensor integrated circuit together; and dicing the bonded wafer into individual cameras; wherein 1.3 is less than the absolute value of (R2 / R1) and the absolute value of (R2 / R1) is less than 2.2.

[0011] In some embodiments, 1.1 is less than the absolute value of R3 / R1, and the absolute value of R3 / R1 is less than 2.4.

[0012] In some embodiments, the first lens is concave with a radius of 0.5 mm; the second lens is convex with a radius of 0.3 mm.

[0013] In some embodiments, the Abbe number of the first lens and the second lens is less than 60.

[0014] In some embodiments, the method further includes forming a first spacer and a second spacer, wherein during the stacking step, the first spacer is located between L1 and L2, and the second spacer is located between L3 and the wafer of the image sensor integrated circuit.

[0015] In some embodiments, the first spacer and the second spacer are formed independently of the L1, L2 and L3 lenses.

[0016] In some embodiments, the first spacer and the second spacer are respectively formed as spacer arms for the L1 lens and the L3 lens.

[0017] In some embodiments, the first spacer and the second spacer are respectively formed as spacer arms for an L2 lens and an L3 lens. Attached Figure Description

[0018] Figure 1 This is a diagram of a chip-level camera with three-element lenses on three substrates, based on this design.

[0019] Figure 2 It is similar to Figure 1 An illustration of a chip-scale camera having three-element lenses on three substrates but with spacers integrally formed with the lenses.

[0020] Figure 3A The description is based on Tables 1 and 3. Figure 2 The example demonstrates simulated ray tracing.

[0021] Figure 3B The description is based on Tables 2 and 3. Figure 2 The example is simulated ray tracing.

[0022] Figure 4 The diagram illustrates the manufacturing process. Figure 1 and Figure 2 The flowchart shows the method for using a chip-level camera. Detailed Implementation

[0023] In one embodiment, a multi-lens surface, wafer-level, puddle-type lens system for a compact imaging camera features a wide field of view (FOV 90 to 130 degrees), low F-number, and low distortion, and can be used with visible or near-infrared (NIR) light. In another embodiment, the lens system has three lens surfaces and an overall diameter of less than 3 millimeters, making it useful in many other applications such as endoscopes, ductoscopes, chip-level cameras for security cameras, and electronic cameras where wide-angle, fixed-focus lenses are desired.

[0024] Chip-level camera 100 ( Figure 1 It uses a compact imaging camera lens system. Figure 1 This is a schematic diagram illustrating the principles disclosed herein and is not intended to imply the dimensions of the various components. The image sensor integrated circuit 102 includes a photoelectric sensor array 107 for capturing images. In an embodiment, the image sensor integrated circuit 102 may include a black mask 104 having an imaging array window 106. The black mask 104 is used to absorb stray light in the area surrounding but not directly in front of the photoelectric sensor array 107 of the image sensor integrated circuit 102.

[0025] In one embodiment, the photoelectric sensor array 107 is a silicon photodiode array, for example, a panchromatic image photodiode array having red, green, and blue filters in a Bayer pattern on its surface. In some other embodiments, the photodiode array has a four-filter pattern with red, green, blue, and infrared filters, allowing four-color red, green, blue, and near-infrared imaging in the visible and infrared spectrum from 380 to 1000 nanometers. In yet another embodiment, the photodiode array is a black-and-white array that is light-sensitive across the full spectrum from 380 to 1000 nanometers.

[0026] The chip-level camera 100 includes a wide-angle lens system with three lenses. The lens system includes a first substrate 116, a second substrate 110, and a third substrate 120. The first substrate 116 is maintained at a predetermined distance from the second substrate 110 via a first spacer 118. The third substrate 120 is maintained at a predetermined distance from the image sensor integrated circuit 102 via a second spacer 111. The first substrate 116 serves as a protective window for the chip-level camera 100, wherein a first surface 117 of the first substrate 116 faces the exterior of the chip-level camera 100.

[0027] A concave L1 lens element 115 is formed on the second surface 119 of the first substrate 116. A first convex L2 lens element 112 is formed on the first surface 122 of the second substrate 110. A black aperture stop 113 with an opening 114 through which light can pass can be formed on the second surface 124 of the second substrate 110 or on the first surface 126 of the third substrate 120. The second substrate 110 and the third substrate 120 are adjacent to each other.

[0028] The second convex L3 lens element 108 is formed on the second surface of the third substrate 120, and the third substrate 120 maintains a predetermined distance from the image sensor integrated circuit 102 through the second spacer 111.

[0029] exist Figure 2 In an alternative embodiment of the illustrated chip-level camera, the second spacer 111 is replaced by a spacer arm 108B formed on the L3 lens element 108A. The first spacer 118 is replaced by a spacer arm 115B formed on the L1 lens element 115A. In another alternative embodiment (not shown), the first spacer 118 is replaced by a spacer arm formed on the L2 element 112 instead of the L1 lens element 115. In yet another embodiment, the second spacer 111 is replaced by a spacer arm 108B formed on the L3 element 108A.

[0030] In one embodiment, lenses L1, L2, and L3 in the lens system of the chip-scale camera 100 are formed using a reflowable moldable polymer with a refractive index NL1 between 1.48 and 1.66 and an Abbe number between 19 and 60, and are transparent to visible light with wavelengths from 400 to 680 nanometers. In a particular embodiment, lens element 115 (L1), lens element 112 (L2), and lens element 108 (L3) are also transparent to near-infrared light with wavelengths from 1000 to 680 nanometers. In some embodiments, lenses L1, L2, and L3 are formed from a reflowable moldable polymer with an Abbe number less than 40.

[0031] L1 lens element 115 has negative refractive power (or refractive power) and has an image-side surface recessed near the optical axis 132. As used herein, "image-side" refers to the side facing the image sensor IC 102, while "object-side" refers to the side facing away from the image sensor IC 102 and towards the object being imaged. In this embodiment, the surface of lens element 115 is aspherical.

[0032] Lens element 112 of L2 has positive refractive power and an object-side surface convex near the optical axis 132. In this embodiment, the surface of lens element 112 is aspherical. An air gap 130 is formed between the first lens L1 and the second lens L2.

[0033] L3 lens element 108 has positive refractive power and an image-side surface that bulges near the optical axis 132. In this embodiment, the surface of lens element 108 is aspherical.

[0034] The black aperture stop 113 is placed between the second substrate 110 and the third substrate 120 in the lens system and includes an aperture opening 114.

[0035] L1 lens element 115 collects wide-angle incident light reflected from the object to be imaged and controls the propagation direction of these rays into the lens system of the chip-scale camera 100. A concave L2 lens element 112 reduces the angle of the light rays entering the system and guides them through aperture 114. The combination of L2 lens element 112 and L3 lens element 108 is used to focus the light rays and guide them to the image plane of the photoelectric sensor array 107. The convex-convex aspherical surfaces of L2 lens element 112 and L3 lens element 108 balance aberrations such as field curvature and distortion. Aperture 114 between L2 lens element 112 and L3 lens element 108 helps reduce aberrations in the lens system.

[0036] In alternative embodiments, additional infrared or other optical filters are provided. Such filters may be deposited on a second surface 124 of the second substrate 110 or a first surface 126 of the third substrate 120. The filters may also be deposited directly on a photodetector array 107 in window 106, which is typically a photodiode array. In one embodiment, the additional infrared optical filter blocks light with wavelengths greater than 700 nanometers.

[0037] Lens element 115 of L1 has a concave aspherical radius of curvature designated R1, and lens element 112 of L2 has a convex aspherical radius of curvature designated R2. In the embodiment, R1 and R2 satisfy the condition:

[0038] 1.3 <ABS(R2 / R1)<2.2

[0039] This condition helps ensure the ratio of refractive power of L2 lens element 112 and L1 lens element 115, thus resulting in a wide field of view in a compact lens system.

[0040] The L3 lens element has a convex aspherical surface with a radius of curvature specified as R3. In the embodiment, R1 and R3 satisfy the following condition:

[0041] 1.1 <ABS(R3 / R1)<2.4

[0042] This condition provides the ratio of the refractive power of the L3 element 108 and the L1 lens element 112, which helps to maintain a smaller principal ray angle and reduce distortion.

[0043] As disclosed herein, the total track length (TTL) of the lens system is defined as the length from the vertex of the object-facing surface (adjacent to substrate 116) of the L1 lens element to the image plane of the photoelectric sensor array 107. The effective focal length of the lens system is defined as f. In the embodiment, TTL and f satisfy the following conditions

[0044] 3 < (TTL / f) < 7

[0045] By limiting the ratio of the total length of the entire lens system to the focal length within a certain range, the total length of the lens system for a specific viewing angle is limited, thus making the overall size of the chip-level camera 100 compact.

[0046] In this embodiment, each of the three aspherical lens elements L1 115, L2 112, and L3 108 is designed according to the aspherical formula:

[0047]

[0048] Where Z is the sag or deviation from the spherical lens, r is the distance from the optical axis of the lens in radians, and k is the quadratic curve parameter with coefficients A4, A6, A8, and A... 10 This describes the deviation of the surface from the axisymmetric quadratic surface specified by the radius of curvature R and k.

[0049] In an exemplary embodiment, lenses L1, L2, and L3 have a refractive index of 1.62, an Abbe number of 26, and the lens parameters are as follows:

[0050] Table 1

[0051] L1 0.352 -3.24 0.818 1.84 2.13 -77.1 287.5 L2 0.657 0.576 0.672 -3.37 56.0 -598 2462 L3 -0.395 -2.06 0.875 -0.702 -8.12 72.5 160

[0052] In an alternative embodiment, lenses L2 and L3 have a refractive index of 1.62 and an Abbe number of 26, while lens L1 has a refractive index of 1.51 and an Abbe number of 60. The lens parameters are as follows:

[0053] Table 2

[0054] L1 0.222 -0.855 0.818 -9.38 146 -3441 46149 L2 0.295 -0.60 0.672 -14.14 806 -32728 746384 L3 -0.492 -15.24 0.875 -6.33 87.5 -148 -5711

[0055] In the representative embodiments described in Tables 1 and 2, which illustrate the principles disclosed herein, the following parameters are also used:

[0056] Table 3

[0057]

[0058] We simulated the lens system described in this paper using the parameters and lens shapes defined in Tables 1 and 3, with ray tracing as follows: Figure 3A As shown, a field of view of 127 degrees, an effective focal length of 0.45 mm, and an f / 2.2 are given. Similar simulations were performed using the parameters and lens shapes defined in Tables 2 and 3, as follows: Figure 3B As shown, the field of view is 99.6 degrees, the effective focal length is 0.52mm, and the aperture is F2.5. In both simulations, chromatic aberration is well corrected.

[0059] Figure 4 This is a flowchart illustrating a method 200 for assembling a chip-level camera 100. Method 200 includes steps 202, 204, 206, 208, 216, and 218. In an embodiment, method 200 further includes at least one of steps 210 and 212.

[0060] An array of lens elements 202, 204, 206 (L1 lens element 115, L2 lens element 112, and L3 lens element 108) is formed on a wafer forming a first substrate 116, a second substrate 110, and a third substrate 120. An aperture stop 208 is formed on the second substrate 110 or the third substrate 120. If individual spacers are used, a wafer with spacers 210, 212 (118, 111) is formed, and a wafer of an image sensor integrated circuit 102 214 is manufactured. These wafers can be manufactured in any order.

[0061] In method 200, an array of L1 lens elements 115 with radius R1 is formed on a first substrate 116. In the example of step 202, the L1 lens elements 115 are formed of a reflowable molding material, wherein 1.55 < refractive index < 1.66.

[0062] In step 204, an array of L2 lens elements 112 with radius R2 is formed on the second substrate 110. In the example of step 204, the L2 lens elements 112 may be formed of a reflowable molding material, wherein 1.55 < refractive index < 1.66.

[0063] In step 206, an array of L3 lens elements 108 with radius R3 is formed on the third substrate 120. In the example of step 206, the L3 lens elements 108 are formed of a reflowable molding material, wherein 1.46 < refractive index < 1.56.

[0064] In one embodiment, a lens is formed by depositing a reflowable moldable material, applying a wafer-sized mold having a negative image of the lens, and reflowing the reflowable moldable material. In some embodiments, such as in Figure 2 The lens extension spacers 108A and 115A shown may also be formed as part of the L1 and / or L3 lens formations in steps 202 and 206, or as part of the L2 and / or L3 lens formations in steps 204 and 206.

[0065] In step 208, a black aperture 113 including the aperture opening 114 can be formed by deposition and etching on the third substrate 120 or the second substrate 110.

[0066] In optional steps 210 and 212, Figure 1 The spacers 118 and 111 can be formed in separate molded wafers.

[0067] The wafer of the image sensor integrated circuit 102 can be manufactured as is known in the field of image sensor integrated circuits 214.

[0068] Assembling and bonding component wafers together 216 to form an array 216 of chip-level cameras 100, wherein a substrate with lenses, spacers and integrated circuit wafers are stacked, such that the substrate, spacers (if used) and lenses are arranged in the order illustrated in Figure 1 and Figure 2 : a first substrate 116 carrying an L1 lens 115, a first spacer 118, a second substrate 110 carrying an L2 lens 112, a third substrate 120 carrying an L3 lens 108, and a second spacer 111 in front of a wafer of an array image sensor integrated circuit 102. The stack is bonded together 216.

[0069] In step 218, after all the wafers and spacers are bonded together, individual chip cube-level cameras 100 are separated or cut (for example, by sawing). Other cutting methods may be used.

[0070] In a specific embodiment, the L1 lens is concave and has a radius of 0.5 mm; the L2 lens is convex and has a radius of 0.3 mm; the L3 lens is convex and has a radius of 0.22 mm.

[0071] Combinations

[0072] The features described herein can be combined in various ways. The contemplated combinations are as follows:

[0073] A chip-level camera designated as A, comprising an image sensor; a concave L1 lens element on an inner surface of a first substrate; a convex L2 lens element on a first surface of a second substrate; an aperture stop disposed on a second surface of the second substrate or on a first surface of a third substrate, the aperture stop being located between the second substrate and the third substrate; a convex L3 lens element on a second surface of the third substrate spaced apart from the image sensor; a first spacer maintaining a predetermined distance between the first substrate and the second substrate; and a second spacer maintaining a predetermined distance between the second substrate and the image sensor. In an embodiment, the lens element L1 has a concave aspherical radius R1, and the lens L2 has a convex aspherical radius R2, such that 1.3 < ABS(R2 / R1) < 2.2 and / or the lens L3 has a convex aspherical radius R3, wherein 1.1 < ABS(R3 / R1) < 2.4.

[0074] A chip-level camera designated as AA, comprising the chip-level camera designated as A, wherein the lens element L1 has a concave aspherical curvature radius R1, and the lens L2 has a convex aspherical curvature radius R2, such that 1.3 is less than the absolute value of R2 divided by R1, and the absolute value of R2 divided by R1 is less than 2.2.

[0075] A chip-level camera designated AB includes a chip-level camera designated A or AA, wherein a lens L3 has a convex aspherical surface with radius R3, wherein 1.1 is less than the absolute value of R3 divided by R1, and the absolute value of R3 divided by R1 is less than 2.4.

[0076] A chip-level camera designated AC includes a chip-level camera designated A, AA, or AB, wherein lenses L1, L2, and L3 are formed of a reflowable moldable polymer with a refractive index between 1.48 and 1.66, and in a particular embodiment 1.61, and an Abbe number between 19 and 60. In some embodiments, the Abbe number of lenses L1, L2, and L3 is less than 40.

[0077] A chip-level camera designated AD, comprising a chip-level camera designated A, AA, AB or AC, wherein a first spacer and a second spacer are respectively formed as spacer arms for L1 and L3 lenses.

[0078] A chip-level camera designated AE includes a chip-level camera designated A, AA, AB, or AC, wherein a first spacer and a second spacer are respectively formed as spacer arms for L2 and L3 lenses.

[0079] Modifications to the above methods and systems may be made without departing from the scope of the invention. Therefore, it should be noted that the content contained in the above specification or shown in the drawings should be interpreted as illustrative rather than restrictive. The following claims are intended to cover all general and specific features described herein, and all statements regarding the scope of the inventive methods and systems that are linguistically appropriate to both.

Claims

1. A chip-level camera, comprising: Image sensor integrated circuit with photoelectric sensor array; A concave L1 lens element formed on the inner surface of the first substrate; A convex L2 lens element formed on the first surface of the second substrate; An aperture stop is formed on the second surface of the second substrate or the first surface of the third substrate, the aperture stop being between the second substrate and the third substrate; A convex L3 lens element formed on the second surface of the third substrate spaced apart from the image sensor integrated circuit; A first spacer configured to maintain a predetermined distance between the first substrate and the second substrate; and A second spacer configured to maintain a predetermined distance between the second substrate and the image sensor integrated circuit; Lens element L1 has a concave aspherical radius R1, and lens L2 has a convex aspherical radius R2, such that 1.3 is less than the absolute value of R2 divided by R1, and the absolute value of R2 divided by R1 is less than 2.

2.

2. The chip-level camera according to claim 1, wherein the lens L3 has a convex aspherical surface with radius R3, wherein 1.1 is less than the absolute value of R3 divided by R1, and the absolute value of R3 divided by R1 is less than 2.

4.

3. The chip-level camera of claim 2, wherein the lenses L1, L2 and L3 are formed of a reflowable moldable polymer with a refractive index between 1.48 and 1.66 and an Abbe number between 19 and 60.

4. The chip-level camera according to claim 3, wherein the first spacer and the second spacer are respectively formed as spacer arms of the L1 lens and the L3 lens.

5. The chip-level camera according to claim 3, wherein the first spacer and the second spacer are respectively formed as spacer arms of the L2 lens and the L3 lens.

6. The chip-level camera of claim 3, wherein the first spacer and the second spacer are formed as separate spacer wafers.

7. A method for manufacturing a chip cube camera, comprising: An array of first lenses having a first radius (R1) of a reflowable molding material is formed on a first substrate, wherein the refractive index of the reflowable molding material is between 1.48 and 1.66; An array of second lenses having a second radius (R2) of the reflowable molding material is formed on a second substrate; An array of third lenses with a third radius (R3) forming a material that can be reflowed and molded; An aperture stop is formed on the second or third substrate; Chips for manufacturing integrated circuits for image sensors; The substrate with lenses and the wafer of the image sensor integrated circuit are stacked sequentially, such that L1 precedes L2, L2 precedes L3, and L3 precedes the image sensor integrated circuit. Connecting the lens and the chip of the image sensor integrated circuit together; and The connected chips are cut into individual cameras; 1.3 is less than the absolute value of (R2 / R1), and the absolute value of (R2 / R1) is less than 2.

2.

8. The method of claim 7, wherein 1.1 is less than the absolute value of R3 / R1, and the absolute value of R3 / R1 is less than 2.

4.

9. The method according to claim 8, wherein the first lens is concave and has a radius of 0.5 mm; and the second lens is convex and has a radius of 0.3 mm.

10. The method of claim 8, wherein the Abbe number of the first lens and the second lens is less than 60.

11. The method of claim 8, further comprising forming a first spacer and a second spacer, wherein during the stacking step, the first spacer is located between L1 and L2, and the second spacer is located between L3 and the wafer of the image sensor integrated circuit.

12. The method of claim 11, wherein the first spacer and the second spacer are formed independently of the L1, L2 and L3 lenses.

13. The method according to claim 11, wherein the first spacer and the second spacer are respectively formed as spacer arms of L1 lens and L3 lens.

14. The method according to claim 11, wherein the first spacer and the second spacer are respectively formed as spacer arms of an L2 lens and an L3 lens.

Images