Flare inhibition image sensor

Abstract

Embodiments disclosed herein reduce petal flare. A flare-suppressed image sensor is provided. The flare-suppressed image sensor includes a plurality of pixels including a first set of pixels and a second set of pixels. The flare-suppressed image sensor also includes a plurality of microlenses, where each microlens is aligned with a respective pixel in the first set of pixels. The flare-suppressed image sensor also includes a plurality of sub-microlenses, where each microlens array is aligned with a respective pixel in the second set of pixels.

Description

Technical Field

[0001] This invention relates to a flare suppression image sensor. Background Technology

[0002] Camera modules in commercial products such as standalone digital cameras, mobile devices, automotive parts, and medical devices include image sensors with pixel arrays. A pixel array comprises multiple pixels arranged in a two-dimensional periodic array. Many image sensors include microlens arrays formed by multiple microlenses, each aligned with a corresponding pixel. The periodicity of the pixel array and the microlens array on it causes the image sensor to resemble a reflective two-dimensional diffraction grating. A portion of the light incident on the image sensor is diffracted onto the camera's imaging lens. Various elements of the camera, such as the cover glass, infrared cutoff filter, and the surface of the imaging lens, reflect this diffracted light back to the image sensor, producing image artifacts known as petal flares. Summary of the Invention

[0003] The embodiments disclosed herein reduce petal flares. This invention provides a flare suppression image sensor. The flare suppression image sensor includes a plurality of pixels, comprising a first group of pixels and a second group of pixels. The flare suppression image sensor also includes a plurality of microlenses, wherein each microlens is aligned with a corresponding pixel in the first group of pixels. The flare suppression image sensor further includes a plurality of sub-microlens arrays, wherein each sub-microlens array is aligned with a corresponding pixel in the second group of pixels.

[0004] In some embodiments, the first group of pixels and the second group of pixels are arranged periodically such that every X pixels from the first group of pixels are followed by Y pixels from the second group of pixels, where X and Y are positive integers.

[0005] In some embodiments, X is greater than Y.

[0006] In some embodiments, X equals 1, and Y equals 2.

[0007] In some embodiments, each sub-microlens has a width between half a micrometer and 3 micrometers.

[0008] In some embodiments, each microlens has a width between 5 micrometers and 1 millimeter.

[0009] In some embodiments, the width of each microlens is approximately twice the width of each submicrolens.

[0010] In some embodiments, the width of each microlens is approximately three times the width of each sub-microlens.

[0011] In some embodiments, the first group of pixels and the second group of pixels are arranged periodically to sufficiently reduce the accumulation of petal flares.

[0012] In some embodiments, each sub-microlens array is arranged as an M×N array, where M and N are values ​​greater than 1.

[0013] In some embodiments, M equals N.

[0014] In some embodiments, M is not equal to N.

[0015] In some embodiments, the plurality of pixels are located within a semiconductor substrate, wherein each of the plurality of microlenses and each of the plurality of sub-microlens arrays are located in a microlens plane above the semiconductor substrate, wherein the image sensor includes a color filter array (CFA) between the microlens plane and the semiconductor substrate, the CFA including a plurality of color filters arranged in a Bayer pattern.

[0016] In some embodiments, each pixel of the first group of pixels has one of the red or blue filters of the Bayer pattern, and each pixel of the second group of pixels has a green filter of the Bayer pattern.

[0017] In some embodiments, the plurality of pixels are located within a semiconductor substrate, wherein each of the plurality of microlenses and each of the plurality of sub-microlens arrays are located in a microlens plane above the semiconductor substrate, wherein the image sensor includes a color filter array (CFA) between the microlens plane and the semiconductor substrate, wherein each filter of the CFA is one of a red filter, a green filter, a blue filter, a cyan filter, a magenta filter, a yellow filter, and a panchromatic filter.

[0018] In some embodiments, the first group of pixels and the second group of pixels are arranged randomly. Attached Figure Description

[0019] Figure 1 A camera for imaging a scene according to an embodiment is depicted.

[0020] Figure 2 and 3 Is as Figure 1 A schematic diagram of the pixel array of an image sensor embodiment for flare suppression.

[0021] Figures 4 to 6 A side view of a pixel sequence aligned with a microlens or sub-microlens array according to an embodiment is shown.

[0022] Figure 7Three cases of pixel arrays aligned with microlenses or sub-microlens arrays are shown.

[0023] Figure 8 This is a graph showing the second-order diffraction of varying wavelengths under three different conditions according to an embodiment. Detailed Implementation

[0024] Petal flares occur when light is scattered from one lens in an image sensor onto another, distorting the image. For example, light can interfere with nearby lenses when it is reflected, diffracted, or incident on them. One aspect of this embodiment includes the understanding that the primary source of petal flares is light incident on and focused by lenses or microlenses of adjacent pixels. Embodiments of this disclosure reduce petal flares by arranging pixels in alignment with alternating microlenses and sub-microlenses. This embodiment reduces petal flares by including a plurality of sub-microlenses (a sub-microlens array) aligned with alternating pixels, wherein each sub-microlens transmits a portion of the light incident on the refractive element of each sub-microlens. In some embodiments, instead of having alternating pixels aligned with microlenses and the sub-microlens array, the arrangement of pixels can be another periodic pattern or randomness to sufficiently reduce petal-flare accumulation within the image sensor.

[0025] Microlenses can be lenses with a width ranging from 10 micrometers to 1 millimeter, while submicrolenses can be lenses with a width ranging from half a micrometer to 3 micrometers.

[0026] Figure 1 An image sensor 100 is shown, which includes a pixel array 154. Figure 1 In the depicted scenario, image sensor 100 is incorporated into camera 190, which images the scene. Camera 190 includes image sensor 100, which includes pixel array 154. Image sensor 100 may be part of a chip-scale package or an on-board chip package.

[0027] Figure 2 It is the pixel array 200 of the flare suppression image sensor (e.g., image sensor 100). Figure 1 A schematic diagram of a portion of the pixel array 154. Figure 2The illustrated pixel array 200 includes pixels 202, 204 and pixels 210, 212, with pixels 202 and 204 each aligned with microlens 206, and pixels 210 and 212 each aligned with an array of sub-microlenses 214. Sub-microlenses 214 may have approximately half (e.g., between 40% and 60%) the width and approximately half (e.g., between 40% and 60%) the radius of curvature of microlenses 206. Furthermore, sub-microlenses 214 are arranged in a 2×2 array within the surface regions of pixels 210 and 212. However, in some embodiments, the sub-microlens array 214 may be an N×N array, where N is any integer greater than 1. For example, an N×N microlens array may be a 3×3 array, a 4×4 array, or any integer N sufficient to reduce petal-flare accumulation.

[0028] For example, Figure 3 This is a schematic diagram of a pixel array 300 (e.g., a portion of pixel array 154) of a flare suppression image sensor (e.g., image sensor 100). Figure 3 The system includes pixels 302, 304 and pixels 310, 312, with pixels 302 and 304 each aligned with microlens 206, and pixels 310 and 312 each aligned with sub-microlenses 314. The sub-microlenses 314 are arranged in a 3×3 array. Each sub-microlens 314 may have approximately one-third (e.g., between 20% and 45%) the width and radius of curvature of microlens 206. The height, radius, and geometry of the sub-microlenses 314 can be varied to sufficiently reduce petal-flare buildup and are not limited to the embodiments of this disclosure.

[0029] Pixel arrays 200 and 300 can be organized into columns and rows, and each row can include a first group of pixels aligned with a microlens and a second group of pixels aligned with an N×N array of sub-microlenses. The arrangement of the first and second groups of pixels within a row can be periodic or random. For example, the arrangement alternates between (i) pixels from the first group of pixels and (ii) adjacent pixels from the second group of pixels. The arrangement can be two pixels from the first group of pixels followed by two pixels from the second group of pixels. And / or the arrangement can include one pixel from the first group of pixels followed by two pixels from the second group of pixels. Typically, the arrangement of the first and second groups of pixels can be periodic or random.

[0030] Figure 4-6 Each shows a portion of an image sensor (e.g., image sensor 100) comprising three pixels, and shows different arrangements of the first group of pixels and the second group of pixels, or different N×N arrays of sub-microarrays within pixels. Figure 4This is a schematic diagram of a portion of an image sensor 400 including three pixels 402, 404, and 406, where pixels 402 and 406 are aligned with microlens 206, and pixel 404 is aligned with sub-microlens 214. The image sensor 400 may include one or more layers, examples of which include a spectral filter array, a passivation layer, and an oxide layer.

[0031] Image sensor 400 includes deep trench isolation layers 418 and 420 between adjacent pixels, the depth of which can vary within a semiconductor substrate 422. In one embodiment, the deep trench isolation layers 418 and 420 comprise oxide. The deep trench isolation layers 418 and 420 have a width 424, which can be at least 150 nm, such that light incident on the deep trench isolation layers 418 and 420 undergoes total internal reflection and is not transmitted to adjacent pixels. The semiconductor substrate 422 has a top surface 416.

[0032] Microlens 206 may be an oxide and fabricated using chemical vapor deposition. In embodiments, microlens 206 is formed of a material (e.g., glass) having a transition temperature between 140°C and 180°C, enabling it to withstand the temperatures of reflow processes associated with an image sensor (e.g., image sensor 100). In some embodiments, sub-microlens 214 comprises a material substantially similar to or the same as microlens 206. In some embodiments, sub-microlens 214 comprises a material different from microlens 206.

[0033] Each sub-microlens 214 may have a height peak, which is determined such that each sub-microlens 214 has a back focal length equal to the thickness 430 of the top surface 416. In some embodiments, the height 426 of the microlens 206 is twice the height of the sub-microlens 214. In some embodiments, the ratio of the height 426 of the microlens 206 to the height of the sub-microlens 214 is a value sufficient to reduce petal-flare buildup. For example, the height of the sub-microlens 214 is between 30% and 70% of the height 426 of the microlens 206. Similarly, the ratio of the width 428 of the base of the microlens 206 to the width of the base of the sub-microlens 214 may be a value sufficient to reduce petal-flare buildup. In embodiments, the width 428 and the width of the lens 214 may be the maximum width in the same direction. In some embodiments, the width 428 is approximately twice the width of the base of the sub-microlens 214. For example, the width of the sub-microlens 214 is between 30% and 70% of the width 428. In the embodiment, the width 428 is between 5 micrometers and 1 millimeter, while the width of the sub-microlens 214 is between half a micrometer and 3 micrometers.

[0034] Figure 5 and Figure 6This is a schematic diagram of portions of image sensors 500 and 600, each of which includes three pixels and is a variation of image sensor 400. Image sensors 500 and 600 may include one or more layers, examples of which include spectral filter arrays, passivation layers, and oxide layers. Pixels 502, 602, and 606 are aligned with microlens 206, respectively, while pixels 504, 506, and 604 are aligned with sub-microlenses 214 and 314, respectively. Semiconductor substrates 524 and 624 have top surfaces 518 and 618, respectively. They are best viewed together in the following description. Figure 5 and Figure 6 .

[0035] Image sensors 500 and 600 differ from image sensor 400 at least in the periodic arrangement of the microlenses and sub-microlenses aligned with pixels 502-506 and 602-606. For example, image sensor 500 includes a different sequence of microlenses 206 and sub-microlenses 214. As can be seen, instead of microlenses 206 being adjacent to sub-microlenses 214 as in image sensor 400, image sensor 500 has the following sequence: pixel 502 aligned with microlens 206, followed by two pixels 504 and 506 aligned with sub-microlenses 214. This sequence can continue for each row of pixels in the image sensor pixel array. Furthermore, each row (not shown) can have a shift relative to adjacent rows within the pixel array in the pixel sequence. For example, the first row of pixels can begin with the sequence in image sensor 500: pixel 502 aligned with microlens 206, followed by two pixels 504 and 506 aligned with sub-microlenses 214, as... Figure 5 As shown. The second row (not shown) may begin with the pixel aligned with sub-microlens 214 (e.g., pixel 504), followed by the pixel aligned with sub-microlens 214 (e.g., pixel 506), followed by the pixel aligned with microlens 206 (e.g., pixel 502). And the third row may continue, such that... Figure 5 The image sensor 500, as shown, shifts the pixels one pixel to the right for each subsequent row. Alternatively, the second row could begin with a pixel aligned with sub-microlens 214, followed by pixels aligned with microlens 206, and... Figure 5 The pixel sequence shown can continue. In an embodiment, any arrangement (periodic or random) of the pixel sequence aligned with the corresponding microlens or sub-microlens is considered such that the arrangement sufficiently reduces petal-flare accumulation.

[0036] Similarly, image sensor 600 exhibits a pixel sequence similar to that of image sensor 400, i.e., pixels aligned with microlens 206 and pixels aligned with sub-microlens 314 are adjacent; however, sub-microlens 314 is arranged in a 3×3 array. Figure 4 ,5 Similar to the available permutations in the present disclosure, the available permutations considered in this disclosure allow for a sufficient reduction in petal-flare accumulation. For example, the first row may include... Figure 6 The rows shown, and the second row of pixels in the image sensor 600, may begin with pixels aligned with sub-microlens 314, followed by pixels aligned with microlens 206, and so on. Embodiments of this disclosure are not limited to those shown. Figures 4 to 6 It can include any permutation and any N×N sub-microlens array, where N is any integer greater than 1. For example, pixel rows can include... Figure 5 The pixel sequence shown is different, but each pixel aligned with sub-microlens 214 can have a 3×3, 4×4, 5×5, or similar array. In some embodiments, any 9×9 pixel array aligned with microlens 206, sub-microlenses 214, 314, etc., can include any combination of image sensors 400, 500, 600. For example, a 9×9 array of sensor elements can include one of each of image sensors 400, 500, 600, two of image sensors 400, 500, 600, one of the image sensors can be rotated such that pixel rows within the image sensor can become columns, and so on.

[0037] Figure 7 Cases 1-3 are illustrated, each depicted as a 2×2 pixel array aligned with a corresponding microlens (e.g., microlens 206) or sub-microlens (e.g., sub-microlens 214). In some embodiments, Bayer filters may be used, and each pixel may be one of a green, red, or blue filter. For example, case 1 illustrates a 2×2 pixel array, with each pixel aligned with a microlens. Case 1 further illustrates a first pixel 702 having a first pattern indicating a blue filter; a second pixel 704 having a second pattern indicating a green filter; a third pixel 706 having a second pattern indicating a green filter; and a fourth pixel 708 having a third pattern indicating a red filter.

[0038] Case 2 illustrates a 2×2 pixel array, where the first and second rows of pixels each include pixels 712 and 714 aligned with microlenses and pixels 710 and 716 aligned with sub-microlenses. Case 2 uses the same patterns corresponding to the red, green, and blue filters of the Bayer filter used in Case 1. For example, pixel 710 has a first pattern indicating the blue filter; pixels 712 and 714 have a second pattern indicating the green filter; and pixel 716 has a third pattern indicating the red filter. Case 3 includes pixels aligned with either microlenses or sub-microlenses. Case 3 features microlenses and sub-microlenses that switch the colors of the Bayer filter as seen in Case 2. For example, the pixels have the same patterns as in Case 2; however, pixel 718 is now aligned with a microlens; pixels 720 and 722 are aligned with sub-microlenses; and pixel 726 is aligned with a microlens.

[0039] Figure 8 A graph 800 showing the second-order diffraction of light in the wavelength range from 400 nm to 700 nm is presented, including diffraction measurements 810, 820, and 830, corresponding to cases 1, 2, and 3, respectively, as shown in Figure 840. Diffraction measurements 820 and 830 show that, compared to diffraction measurement 810, the second-order diffraction of light is significantly reduced for all wavelengths except in the 410 nm region. Furthermore, diffraction measurements 820 and 830 remain approximately consistent until about 590 nm, after which they diverge. The difference between diffraction measurements 820 and 830 can be attributed to the color of the Bayer filter covered by the microlens or sub-microlens. In some embodiments, color filter arrays other than Bayer filters can be used, such as RGBE filters, RYYB filters, CYYM filters, CYGM filters, RGBW filters, X-Trans filters, Quad Bayer filters, RYYB Quad filters, Nonacell filters, RCCC filters, RCCB filters, etc. In some embodiments, each filter in the color filter array may include one or more of a red filter, a green filter, a blue filter, a cyan filter, a magenta filter, a yellow filter, and a panchromatic filter. In some embodiments, the image sensor includes a color filter array (CFA) located between a sub-microlens array and a semiconductor substrate, and the CFA includes a plurality of color filters arranged in a Bayer pattern.

[0040] The above description presents, in full, clear, concise, and precise terminology, the best mode contemplated for performing these embodiments, as well as the ways and procedures for practicing them, so that any person skilled in the art to which these embodiments pertains can practice them. However, these embodiments are readily adapted from the above discussion with fully equivalent modifications and alternative constructions. Therefore, the invention is not limited to the specific embodiments disclosed. Rather, the invention encompasses all modifications and alternative constructions within the spirit and scope of this disclosure. For example, the arrangement / sequence of pixel or microlens arrays described herein need not be formed in the same structure as they have been presented, and can be formed in any manner. Furthermore, in alternative embodiments, structures that have been presented as being formed separately can be formed simultaneously. Similarly, in alternative embodiments, structures that have been presented as being formed simultaneously can be formed separately.

[0041] Feature combination

[0042] Specifically, the following embodiments are envisioned, as well as any combination of these embodiments that are compatible with each other:

[0043] (A) A flare suppression image sensor includes a plurality of pixels, comprising a first group of pixels and a second group of pixels. The flare suppression image sensor also includes a plurality of microlenses, each microlens being aligned with a corresponding pixel in the first group of pixels. The flare suppression image sensor also includes a plurality of sub-microlens arrays, each sub-microlens array being aligned with a corresponding pixel in the second group of pixels.

[0044] (B) In the embodiment represented by (A), the first group of pixels and the second group of pixels are arranged periodically such that every X pixels from the first group of pixels are followed by Y pixels from the second group of pixels, where X and Y are both positive integers.

[0045] (C) In the embodiment represented by (B), X is greater than Y.

[0046] (D) In ​​the embodiment represented by (B), X equals 1 and Y equals 2.

[0047] (E) In the embodiment represented by (A), each sub-microlens has a width between half a micrometer and 3 micrometers.

[0048] (F) In the embodiment represented by (A), each microlens has a width between 5 micrometers and 1 millimeter.

[0049] (G) In the embodiment represented by (A), the width of each microlens is approximately twice the width of each sub-microlens.

[0050] (H) In the embodiment represented by (A), the width of each microlens is approximately three times the width of each sub-microlens.

[0051] (I) In the embodiment represented by (A), the first group of pixels and the second group of pixels are periodically arranged to sufficiently reduce the accumulation of petal flares.

[0052] (J) In the embodiment represented by (A), each sub-microlens array is arranged as an M×N array, where M and N are values ​​greater than 1.

[0053] (K) In the embodiments represented by (A) and (J), M equals N.

[0054] (L) In the embodiments represented by (A) and (J), M is not equal to N.

[0055] (M) In the embodiment represented by (A), multiple pixels are located within a semiconductor substrate. Each of the multiple microlenses and each of the multiple sub-microlens arrays are located in a microlens plane above the semiconductor substrate. The image sensor includes a color filter array (CFA) between the microlens plane and the semiconductor substrate, the CFA comprising multiple color filters arranged in a Bayer pattern.

[0056] (N) In the embodiments shown in (A) and (M), each pixel of the first group of pixels has one of a red or blue filter with a Bayer pattern, while each pixel of the second group of pixels has a green filter with a Bayer pattern.

[0057] (O) In the embodiment represented by (A), a plurality of pixels are located within a semiconductor substrate. Each of a plurality of microlenses and each of a plurality of sub-microlens arrays are located in a microlens plane above the semiconductor substrate. The image sensor includes a color filter array (CFA) between the microlens plane and the semiconductor substrate. Each filter of the CFA is one or more of a red filter, a green filter, a blue filter, a cyan filter, a magenta filter, a yellow filter, and a panchromatic filter.

[0058] (P) In the embodiment represented by (A), the first group of pixels and the second group of pixels are randomly arranged.

Claims

1. A flare-inhibiting image sensor, comprising: a plurality of image sensor pixels within a semiconductor substrate, the plurality of image sensor pixels including a first set of pixels and a second set of pixels; a plurality of microlenses, each microlens (i) being located within a microlens plane above the semiconductor substrate, (ii) being aligned with a respective one of the first set of pixels; a plurality of sub-microlens arrays, each sub-microlens array (i) being located within the microlens plane, (ii) being aligned with a respective one of the second set of pixels, and (iii) including a plurality of sub-microlenses, each sub-microlens having a width between one-half micrometer and three micrometers, less than a width of each microlens of the plurality of microlenses; and a color filter array (CFA) between the microlens plane and the semiconductor substrate, wherein each filter of the CFA is one of a red filter, a green filter, a blue filter, a cyan filter, a magenta filter, a yellow filter, and a panchromatic filter; none of the plurality of microlenses is aligned with any pixel of the second set of pixels, none of the plurality of sub-microlens arrays is aligned with any pixel of the first set of pixels.

2. The flare-inhibiting image sensor of claim 1, wherein the first set of pixels and the second set of pixels are periodically arranged such that every X pixels from the first set of pixels is followed by Y pixels from the second set of pixels, where X and Y are positive integers.

3. The flare-inhibiting image sensor of claim 2, wherein X is greater than Y.

4. The flare-inhibiting image sensor of claim 2, wherein X is equal to one and Y is equal to two.

5. The flare-inhibiting image sensor of claim 1, wherein each microlens has a width between five micrometers and one millimeter.

6. The flare-inhibiting image sensor of claim 1, wherein a width of each microlens is approximately twice a width of each sub-microlens.

7. The flare-inhibiting image sensor of claim 1, wherein a width of each microlens is approximately three times a width of each sub-microlens.

8. The flare-inhibiting image sensor of claim 1, wherein the first set of pixels and the second set of pixels are periodically arranged to substantially reduce petal flare buildup.

9. The flare-inhibiting image sensor of claim 1, wherein each sub-microlens array is arranged in an M x N array, where M and N are values greater than one.

10. The flare-inhibiting image sensor of claim 9, wherein M is equal to N.

11. The flare-inhibiting image sensor of claim 9, wherein M is not equal to N. ​ 12. The flare-inhibiting image sensor of claim 1, wherein the plurality of image sensor pixels are located within a semiconductor substrate, wherein each of the plurality of microlenses and each of the plurality of sub-microlens arrays are located within a microlens plane above the semiconductor substrate, wherein the image sensor includes a color filter array (CFA) between the microlens plane and the semiconductor substrate, the CFA including a plurality of color filters arranged in a Bayer pattern.

13. The flare-inhibiting image sensor of claim 12, wherein each pixel of the first group of pixels has one of a red or blue filter of the Bayer pattern, and wherein each pixel of the second group of pixels has a green filter of the Bayer pattern.

14. The flare-inhibiting image sensor of claim 1, wherein the first group of pixels and the second group of pixels are arranged randomly.

15. The flare-inhibiting image sensor of claim 1, further comprising: a pixel array including each of the plurality of image sensor pixels, the plurality of microlenses including a first microlens aligned with a first pixel of the first group of pixels; the plurality of sub-microlens arrays including a first sub-microlens array that is (i) aligned with a second pixel of the second group of pixels adjacent to the first pixel, and (ii) coplanar with the first microlens in a plane parallel to the pixel array.

16. A flare-inhibiting image sensor, comprising: a semiconductor substrate having a pixel array including a first group of image sensor pixels and a second group of image sensor pixels; a plurality of microlenses each (i) located within a microlens plane above the semiconductor substrate, (ii) aligned with a respective image sensor pixel of the first group of image sensor pixels; a plurality of sub-microlens arrays each (i) located within the microlens plane, (ii) aligned with a respective pixel of the second group of image sensor pixels, and (iii) including a plurality of sub-microlenses each having a width between half a micrometer and 3 micrometers, less than a width of each microlens of the plurality of microlenses; and the plurality of microlenses including a first microlens aligned with a first pixel of the first group of image sensor pixels, a color filter array (CFA) between the microlens plane and the semiconductor substrate, wherein each filter of the CFA is one of a red filter, a green filter, a blue filter, a cyan filter, a magenta filter, a yellow filter, and a panchromatic filter; the plurality of sub-microlens arrays including a first sub-microlens array that is (i) aligned with a second pixel of the second group of image sensor pixels adjacent to the first pixel, and (ii) coplanar with the first microlens in a plane parallel to the pixel array.

Images