Image sensor, imaging module and electronic equipment

Abstract

The invention provides an image sensor, an imaging module and electronic equipment, and belongs to the technical field of optical imaging, the image sensor comprises a plurality of photosensitive modules arranged in an array and reflection units in one-to-one correspondence with the photosensitive modules, and each photosensitive module comprises a photosensitive unit and a reading circuit; the reflection unit and the readout circuit are arranged at an interval, and the reflection unit is used for reflecting at least part of the light transmitted from the readout circuit to the light sensing unit so as to enhance the effective light receiving efficiency of the light sensing unit. And the fill factor can be effectively improved.

Description

Technical Field

[0001] The present disclosure relates to the field of optical imaging technology, and in particular to an image sensor, an imaging module, and an electronic device. Background Art

[0002] Image sensors, as core semiconductor components for photoelectric conversion, use complementary metal oxide semiconductors (CMOS) to convert optical signals into electrical signals. Their performance directly impacts the image quality of cameras, smartphones, medical imaging equipment, and autonomous driving systems. The core operating principle of CMOS is that a photodiode array captures incident photons and generates charge. This charge is then amplified and converted to digital by a readout circuit, ultimately generating processable digital image data.

[0003] Throughout the evolution of sensor architecture, stacked designs have utilized three-dimensional vertical integration technology to stack the photosensitive layer (pixel array) and signal processing layer (logic circuits and memory cells) at the wafer level, interconnecting them using through-silicon vias (TSVs). This three-dimensional architecture not only significantly improves chip area utilization but also effectively avoids the performance bottlenecks of traditional planar structures by physically isolating the photosensitive area from the circuit area. It has become a key technology path for high-end mobile imaging and automotive vision systems.

[0004] Although traditional stacked image sensors, represented by back-illuminated stacked sensors, have achieved optical path optimization, non-photosensitive components such as peripheral circuits (metal interconnect layers) and transistors occupy 30% to 70% of the pixel unit area, making it difficult for the fill factor (i.e., the percentage of the effective photosensitive area of ​​the photosensitive region to the total area of ​​a single pixel) to exceed the 70% threshold. However, the low fill factor causes a decrease in photon utilization, resulting in poor image quality. Summary of the Invention

[0005] The present disclosure provides an image sensor, an imaging module, and an electronic device, which can effectively improve the fill factor.

[0006] The technical solution of the present disclosure is achieved as follows: In a first aspect, the present disclosure provides an image sensor comprising a plurality of array-arranged photosensitive modules and reflective units corresponding one-to-one to the photosensitive modules, wherein the photosensitive modules comprise a photosensitive unit and a readout circuit; the reflective unit is spaced apart from the readout circuit and is configured to reflect at least part of the light transmitted from the readout circuit to the photosensitive unit, so as to enhance the effective light receiving efficiency of the photosensitive unit.

[0007] In a second aspect, the present disclosure further provides an imaging module, which includes an image processing unit and the image sensor of the first aspect; the image processing unit is used to generate image data based on the digital signal output by the image sensor.

[0008] In a third aspect, the present disclosure further provides an electronic device comprising the above-mentioned imaging module.

[0009] The present disclosure provides an image sensor in which a reflective unit is vertically arranged on the backlight side (Z-axis direction) of a readout circuit and maintains a preset distance from the readout circuit. Through a dual-path light capture mechanism of direct reception and reflection recovery, the physical limitations of the fill factor are overcome, and the effective photosensitive area of ​​the photosensitive unit is increased. Thus, while maintaining compatibility with the traditional stacked image sensor process, an improvement in the fill factor is achieved, so that better quality images can be generated even in low-light environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic structural diagram of a traditional back-illuminated image sensor provided by the present invention.

[0011] Figure 2 A schematic structural diagram of an image sensor provided by the present disclosure.

[0012] Figure 3 A schematic structural diagram of an image sensor including two concave reflectors provided by the present disclosure.

[0013] Figure 4 A schematic structural diagram of an image sensor including a light propagation path provided by the present disclosure.

[0014] Figure 5 A schematic structural diagram of another image sensor provided by the present disclosure.

[0015] Figure 6 A schematic diagram of the chief ray angle provided in the present disclosure.

[0016] Figure 7 A schematic diagram of the border and center area of ​​the photosensitive unit provided in the present disclosure.

[0017] Figure 8 A schematic diagram of the design principle of a first concave reflecting mirror provided in the present invention.

[0018] Figure 9 A schematic diagram of the design principle of another first concave reflecting mirror provided in the present invention.

[0019] Figure 10 A schematic diagram of the design principle of a second concave reflecting mirror provided in the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in this disclosure to clearly describe the technical solutions in the embodiments of the present disclosure. Obviously, the embodiments described are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this disclosure.

[0021] The terms "first," "second," and the like in the specification of the present disclosure are used to distinguish similar objects, and are not used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the present disclosure can be implemented in an order other than that illustrated or described herein. Furthermore, the objects distinguished by "first," "second," and the like generally refer to a class of objects, and do not limit the number of objects. For example, the first object may be one or more.

[0022] like Figure 1 As shown, a single pixel unit 10 of a conventional back-illuminated stacked image sensor consists of a photosensitive unit 101 (photodiode) and a photoelectric conversion control circuit 401 (pixel transistor) arranged side by side in the XY plane. Peripheral circuitry 402 is stacked vertically below the pixel array along the Z axis. The operating principle and structural characteristics of a conventional back-illuminated stacked image sensor can be broken down as follows: Located on the top layer of the semiconductor material (the light incident side), after incident light is focused by microlenses and spectrally filtered by color filters, the photon energy is absorbed by the silicon-based material of photosensitive unit 101, exciting electron-hole pairs and forming charge packets proportional to the light intensity, completing the physical conversion of light signals into charge signals. Photoelectric conversion control circuit 401, composed of reset transistors, select transistors, and amplifier transistors, is used to control the charge storage and transfer timing of photosensitive unit 101, perform charge-to-voltage conversion (via floating diffusion nodes), and suppress dark current noise and inter-pixel crosstalk. Peripheral circuit 402 is responsible for quantization and digitization of charge signals, global exposure synchronization and readout timing management, and image data preprocessing (such as noise reduction and gain adjustment).

[0023] Combine Figure 1 It can be seen that in the traditional back-illuminated architecture, although the photosensitive unit 101 is placed at the front end of the light incident path, it is limited by the structural constraints of the photoelectric conversion control circuit 401 and the peripheral circuit 402 integrated on the same plane. Figure 1The ratio of the area of ​​the photosensitive unit 101 to the combined area of ​​the photosensitive unit 101 and the photoelectric conversion control circuit 401 is only 30% to 70%. The low fill factor directly leads to a decrease in quantum efficiency and an increase in noise-equivalent illumination. In low-light scenarios, the limited photosensitive area significantly reduces the number of captured photons, causing the signal intensity to approach the noise floor level of the readout circuit. Photons scattered into non-photosensitive areas may excite random charges, exacerbating fixed-pattern noise and thermal noise, resulting in a sharp decline in image quality in low-light environments.

[0024] Based on the above problems, the present disclosure aims to provide an image sensor that can effectively improve the fill factor, the image sensor comprising a plurality of photosensitive modules arranged in an array and a reflective unit corresponding to the photosensitive modules one by one, such as Figure 2 As shown, a photosensitive module 40 and a corresponding reflecting unit 30 provided by the present disclosure are shown, and each photosensitive module 40 includes a photosensitive unit 101 and a readout circuit 102; the reflecting unit 30 is spaced apart from the readout circuit 102 and is used to reflect at least part of the light transmitted from the readout circuit 102 to the photosensitive unit 101, so as to enhance the effective light receiving efficiency of the photosensitive unit 101.

[0025] The photosensitive unit 101 is a photosensitive element (such as a photodiode) that converts incident light into a charge signal. The readout circuit 102 is used to convert the charge signal into a digital signal. The reflective unit 30 is an optical element corresponding to the photosensitive module 40. It reflects the originally scattered light back to the photosensitive unit 101 through a specific geometric structure (such as a concave mirror or prism). Figure 2 In the figure, the reflecting unit 30 is shown as a concave mirror.

[0026] The reflection unit 30 and the readout circuit 102 are arranged at a predetermined interval in the vertical direction (Z-axis direction shown in the figure) so that the portion that does not overlap with the projection of the photosensitive unit 101 in the vertical direction (such as Figure 2 The transmitted light corresponding to the incident light (the uncovered portion of the photosensitive unit 101 on the right side of the dotted line shown in the figure) can also be reflected by the reflecting unit 30 and reused by the photosensitive unit 101.

[0027] The spacing (Z-axis spacing) between the reflective unit 30 and the readout circuit 102 affects the transmission path of the reflected light, thereby affecting the effective light reception efficiency. For example, a reference distance can be determined based on the curvature of the reflective unit 30 and the target focal length. For example, if the focal length of the reflective unit 30 is 5μm and the thickness of the photosensitive module 40 is 2μm, the reference distance can be set to 5μm - 2μm = 3μm. The final spacing can then be adjusted around 3μm as needed to obtain the final spacing. The specific spacing can also be determined based on the mapping relationship between the actual spacing and the effective light reception efficiency, which is not limited in this disclosure.

[0028] The effective light receiving efficiency refers to the ratio of the incident light energy actually captured by the photosensitive unit 101 to the total incident light energy. When the area of ​​the photosensitive unit 101 remains unchanged, the light transmitted by the readout circuit 102 is reflected to the photosensitive unit 101 and reused by the photosensitive unit 101. When the total incident light energy remains unchanged, the incident light energy increases, thereby improving the effective light receiving efficiency. Figure 2 Part of the incident light 1 shown in FIG. 1 is transmitted to the reflection unit 30 through the readout circuit 102 , and the reflection unit 30 reflects the transmitted light again to the photosensitive unit 101 , so that the light is captured by the photosensitive unit 101 for the second time.

[0029] In some embodiments, the reflection unit 30 is configured to reflect light of a predetermined ratio threshold or higher among the light transmitted by the readout circuit 102 to the photosensitive unit 101. For example, if the predetermined ratio threshold is 70%, at least 70% of the light energy of the transmitted light is reflected to the photosensitive unit 101.

[0030] The preset ratio threshold is used to adjust the optical design (such as optimization of the curvature of the concave mirror) or material selection (such as high-reflectivity metal plating) of the reflection unit 30 to ensure that at least a preset ratio threshold (such as 70%) of the light transmitted from the readout circuit 102 can be directionally reflected to the photosensitive unit 101, thereby significantly improving the effective light receiving efficiency of the photosensitive unit 101.

[0031] The preset ratio threshold can be determined based on the image sensor's application scenario. If the image sensor is used in conventional camera equipment, the preset ratio threshold can be set to a smaller value, such as 50%. If the image sensor is used in night vision equipment, the preset ratio threshold can be set to a larger value, such as 80%. The preset ratio threshold can also be set to 80%, 90%, etc., and can also be customized according to needs.

[0032] In the image sensor provided herein, the reflective unit 30 is positioned perpendicular to the backlight side (Z-axis direction) of the readout circuit 102 and maintains a predetermined distance from the readout circuit 102. This dual-path light capture mechanism, combining direct reception and reflective recycling, overcomes the physical limitations of fill factor and increases the effective photosensitive area of ​​the photosensitive unit 101. This improvement in fill factor is achieved while maintaining process compatibility with conventional stacked image sensors, enabling the generation of high-quality images even in low-light environments.

[0033] In some embodiments, the reflection unit 30 includes at least one concave reflection mirror, which is arranged to be a preset distance away from the readout circuit 102 in a vertical direction perpendicular to the photosensitive surface of the photosensitive unit 101. Figure 3 As shown, the reflecting unit 30 exemplarily includes a first concave reflecting mirror 301 and a second concave reflecting mirror 302 .

[0034] The special curved surface structure (such as a parabola or a sphere) of the concave reflector can directionally reflect and focus the transmitted light incident on its surface. This allows the light that originally penetrated the readout circuit 102 to be reflected by the concave mirror and then re-converge onto the effective photosensitive area of ​​the photosensitive unit 101.

[0035] The preset vertical distance between the concave mirror and the readout circuit 102 is to ensure that the reflected light spot accurately covers the photosensitive unit 101. Figure 3 The vertical distance between the first concave reflector 301 and the second concave reflector 302 and the readout circuit 102 is shown as d1. A distance that is too close can cause the light focus position to deviate from the photosensitive area, while a distance that is too far can cause phase interference and light energy loss due to the optical path difference. Therefore, the preset distance is determined by considering the light focus position, optical path difference, and light energy loss.

[0036] In the present disclosure, since the concave mirror has the ability to converge light, more light transmitted to the reflection unit 30 can be reflected to the photosensitive unit 101, thereby improving the effective light receiving efficiency of the photosensitive unit 101.

[0037] In some embodiments, as Figure 4 As shown, the readout circuit 102 includes a photoelectric conversion control circuit 401 and a peripheral circuit 402. The photoelectric conversion control circuit 401 and the photosensitive unit 101 are arranged in parallel on the same plane and are both attached to one side of the peripheral circuit 402. The reflection unit 30 includes a first concave reflection mirror 301 and a second concave reflection mirror 302. The first concave reflection mirror 301 is used to reflect at least part of the light transmitted through the first concave reflection mirror 301 back to the photosensitive unit 101; the second concave reflection mirror 302 is used to reflect at least part of the light transmitted through the second concave reflection mirror 302 back to the photosensitive unit 101.

[0038] If the reflective unit 30 includes only one concave reflective mirror, due to the inherent characteristics of the concave reflective mirror, once the reflectivity of the transmitted light reaches a threshold, no matter how the parameters of the concave reflective mirror are optimized, the reflected light energy cannot be further increased. Therefore, by providing two concave reflective mirrors, the effective light receiving efficiency of the photosensitive unit 101 is further optimized.

[0039] The first concave reflecting mirror 301 is located on the backlight side of the peripheral circuit 402 and is located within the vertical projection of the photosensitive unit 101. The second concave reflecting mirror 302 is located on the backlight side of the peripheral circuit 402 and is located within the vertical projection of the photoelectric conversion control circuit 401.

[0040] The first concave reflecting mirror 301 can reflect the light incident on the photosensitive unit 101 and the light transmitted through the photosensitive unit 101 and the peripheral circuit 402 to the photosensitive unit 101. Figure 4 or the light incident from the edge of the photoelectric conversion control circuit 401, after the transmission of the photoelectric conversion control circuit 401 and the peripheral circuit 402, is deflected to the first concave reflector 301 and reflected to the photosensitive unit 101, such as Figure 4 The propagation path of light ray 3 in .

[0041] The second concave reflecting mirror 302 can reflect the light incident on the photoelectric conversion control circuit 401 and the light transmitted through the photoelectric conversion control circuit 401 and the peripheral circuit 402 to the photosensitive unit 101. Figure 4 The propagation path of light ray 4 in .

[0042] In some embodiments, the first concave reflecting mirror 301 and the second concave reflecting mirror 302 are spaced apart from the peripheral circuit 402 in the vertical direction, and the first concave reflecting mirror 301 coincides with the projection of the photosensitive unit 101 in the vertical direction, and the second concave reflecting mirror 302 coincides with the projection of the photoelectric conversion control circuit 401 in the vertical direction.

[0043] The projection of the first concave reflecting mirror 301 and the photosensitive unit 101 in the vertical direction coincides, that is, the orthographic projection of the first concave reflecting mirror 301 and the photosensitive unit 101 coincides. The projection of the second concave reflecting mirror 302 and the photoelectric conversion control circuit 401 in the vertical direction coincides, that is, the orthographic projection of the second concave reflecting mirror 302 and the photoelectric conversion control circuit 401 coincides. Figure 5 As shown, the first concave reflector 301 and the second concave reflector 302 are connected, and their orthographic projections coincide with the orthographic projection of the current photosensitive module 40. This arrangement can maximize the reflection of light transmitted through the first concave reflector 301 and the second concave reflector 302 to the photosensitive unit 101, and the orthographic projection of the concave reflector will not intersect with the orthographic projection of the adjacent photosensitive module 40. Therefore, it will not affect the imaging of the adjacent photosensitive module 40, that is, it will not cause crosstalk.

[0044] Because a single concave reflector is limited by its reflection angle coverage and focus shift effects, even after the reflectivity reaches the material's limit, some transmitted light still cannot be effectively recovered. The dual-mirror architecture, however, uses a partitioned reflection mechanism: the first concave reflector 301 is primarily responsible for reflecting light transmitted from the photosensitive unit 101 to the peripheral circuit 402, while the second concave reflector 302 is primarily responsible for reflecting light transmitted from the photoelectric conversion control circuit 401 to the peripheral circuit 402. This improves the light energy utilization rate of the photosensitive unit 101 without changing the basic pixel structure.

[0045] In some embodiments, the curvature and position of the first concave reflector 301 are configured to reflect transmitted light corresponding to incident light with a negative chief ray angle at a boundary position of the photosensitive unit 101 away from the photoelectric conversion control circuit 401, and transmitted light corresponding to incident light with a positive chief ray angle at a boundary position close to the photoelectric conversion control circuit 401, toward the center of the photosensitive unit 101. The positive chief ray angle is the critical angle at which incident light deflects clockwise relative to the vertical direction, and the negative chief ray angle is the critical angle at which incident light deflects counterclockwise relative to the vertical direction. The critical angles range from 0 degrees to 90 degrees.

[0046] Since not all incident light at any angle can be captured by the photosensitive unit 101, the image sensor is designed with a preset maximum allowable angle between the light from the lens to the photosensitive surface of the photosensitive unit 101 and the normal to the photosensitive surface. That is, the principal ray angle is the critical angle of the incident light that can be captured by the photosensitive unit 101. Light incident at an angle exceeding the principal ray angle is not easily captured by the photosensitive unit 101. Figure 6 As shown, the normal line of the photosensitive surface of the photosensitive unit 101 is the Z axis, θ1 is the designed chief ray angle, and the light incident at an angle θ2 greater than θ1 cannot be effectively utilized by the photosensitive unit 101.

[0047] The center area of ​​the photosensitive unit 101 refers to a preset area with the geometric center of the photosensitive surface of the photosensitive unit 101 as the origin. The boundary position of the photosensitive unit 101 refers to four boundaries. Figure 7 As shown, the bold line outside the photosensitive unit 101 is the boundary position of the photosensitive unit 101, and the area shown in the dotted box is the central area.

[0048] like Figure 8 As shown, θ1 is the principal ray angle, boundary 1 is the boundary of the photosensitive unit 101 away from the photoelectric conversion control circuit 401, and boundary 2 is the boundary of the photosensitive unit 101 close to the photoelectric conversion control circuit 401. Light 5 is incident on the photosensitive unit 101 at θ1 from the boundary 1 of the photosensitive unit 101, and the incident angle of light 5 is the negative principal ray angle. Light 6 is incident on the photosensitive unit 101 at θ1 from the boundary 2 of the photosensitive unit 101, and the incident angle of light 6 is the positive principal ray angle. Part of the light of the two beams is transmitted to the first concave reflector 301 and is reflected to the central area P of the photosensitive unit 101. This design ensures that any light incident at an angle less than or equal to the principal ray between the boundary 1 and the center region O is reflected back to the photosensitive unit 101 when it is transmitted through the first concave reflector 301, and that any light incident at an angle less than or equal to the principal ray between the boundary 2 and the center region O is reflected back to the photosensitive unit 101 when it is transmitted through the first concave reflector 301, such as light 7. This ensures that as much light as possible that is transmitted through the first concave reflector 301 is reflected back to the photosensitive unit 101.

[0049] The curvature and position of the first concave reflector 301 can be determined through mathematical calculation based on the refractive index of the photosensitive module 40, the wavelength of the incident light, the thickness of the photosensitive module 40 (the distance between the upper photosensitive surface of the photosensitive unit 101 and the peripheral circuit 402 in the Z-axis direction), and the distance between two opposing boundaries of the photosensitive unit 101. Alternatively, the curvature and position of the first concave reflector 301 can be determined gradually according to a preset adjustment strategy until the transmitted light corresponding to the incident light at the chief ray angle at the boundary of the photosensitive unit 101 is reflected toward the center of the photosensitive unit 101.

[0050] For example, the initial curvature and initial position of the first concave reflector 301 are preliminarily determined using the principles of geometric optics based on the size, principal ray angle, and material refractive index of the photosensitive unit 101. Using optical simulation software, incident light is incident from a boundary point (the center point of each of the four boundaries of the photosensitive unit 101) at a principal ray angle. The reflected light spot is detected to determine whether it is located in the central area of ​​the photosensitive unit 101 (e.g., the central 20% area). The overlap ratio between the reflected light spot and the central area of ​​the photosensitive unit 101 is calculated. Coarse-tuning optimization (coordinated adjustment of curvature and position): Using the initial curvature as a reference, the curvature is adjusted according to a first preset step size. The curvature is detected to see if the reflected light spot shrinks or spreads toward the center, and the curvature direction that improves the light spot overlap is selected. The optimized curvature is fixed, and the position is adjusted according to a second preset step size to determine the optimal focus position (where the light spot is minimized and the center overlap is maximized). The synergistic effect of curvature and vertical distance is detected. For example, the curvature can be increased by 5%, while the position is adjusted and the vertical distance is reduced by 10%. This eliminates combinations where the light spot is dispersed or off-center, retaining the optimal M (integer greater than 1) parameter groups for fine-tuning. Fine-tuning optimization: Near the coarse-tuning optimal curvature, the curvature is fine-tuned with a third preset step size, smaller than the first preset step size, to verify whether the overlap between the light spot and the center area is greater than or equal to a first threshold. Near the coarse-tuning optimal position, the position is adjusted with a fourth preset step size, smaller than the second preset step size, until the light spot is centered. In this way, by alternately adjusting the curvature and the position, the light incident at the edge of the photosensitive unit 101 at the chief ray angle and transmitted to the first concave reflective mirror 301 is reflected to the central area.

[0051] In some embodiments, the first concave reflector 301 is positioned outside the reflection light path of the second concave reflector 302. This design is to prevent the light reflected from the second concave reflector 302 to the photosensitive unit 101 from being blocked by the first concave reflector 301, resulting in the reflected light not being captured by the photosensitive unit 101. Figure 9 As shown, the first concave reflecting mirror 301 is arranged in the reflecting light path of the second concave reflecting mirror 302 , resulting in that the light 8 cannot be captured by the photosensitive unit 101 .

[0052] In some embodiments, the first concave reflector 301 is connected to the second concave reflector 302. Since the energy of light will decay during propagation, the shorter the optical path, the more energy is retained. The first concave reflector 301 should be located outside the reflection light path of the second concave reflector 302. After the position of the second concave reflector 302 is determined, the first concave reflector 301 is connected to the second concave reflector 302, so that the light passing through the second concave reflector 302 is the shortest. Figure 9 The first concave reflecting mirror 301 and the second concave reflecting mirror 302 shown in FIG. 3 are not connected. Figure 8 The first concave reflecting mirror 301 shown in FIG. 3 is connected to the second concave reflecting mirror 302 .

[0053] In some embodiments, the curvature, inclination and position of the second concave reflecting mirror 302 are set to reflect the transmitted light corresponding to the incident light with the forward principal ray angle at the boundary position of the photoelectric conversion control circuit 401 away from the photosensitive unit 101 to the boundary area of ​​the photosensitive unit 101 away from the photoelectric conversion control circuit 401, and the position of the second concave reflecting mirror 302 is set to be the shortest vertical distance from the photoelectric conversion control circuit 401, and the forward principal ray angle is the critical angle for the incident light to be deflected clockwise relative to the vertical direction.

[0054] The border region of the photosensitive unit 101 refers to a predetermined area centered on the border. Since light energy decays during propagation, a shorter optical path results in more energy retention. Therefore, as long as the transmitted light corresponding to incident light at the forward principal ray angle is reflected to the border region of the photosensitive unit 101 away from the photoelectric conversion control circuit 401, it is preferable to position the second concave reflector 302 as close to the photoelectric conversion control circuit 401 as possible.

[0055] like Figure 10 As shown, the boundary position of the photoelectric conversion control circuit 401 away from the photosensitive unit 101 is boundary 3, the forward principal ray angle is the incident angle corresponding to light ray 9, and the inclination angle of the second concave reflector 302 is α. The portion of light ray 9 that is transmitted through the second concave reflector 302 is reflected and captured by the boundary area of ​​the photosensitive unit 101. This design ensures that light incident on the photoelectric conversion control circuit 401 at an angle less than or equal to the principal ray angle, such as light ray 10, can be captured by the photosensitive unit 101 after being reflected by the second concave reflector 302. This ensures that as much light as possible that is transmitted through the second concave reflector 302 is reflected to the photosensitive unit 101.

[0056] The curvature, position, and inclination of the second concave reflector 302 can be determined through mathematical calculation based on the refractive index of the photosensitive module 40, the wavelength of the incident light, the thickness of the photosensitive module 40 (the distance between the upper photosensitive surface of the photosensitive unit 101 and the peripheral circuit 402 in the Z-axis direction), and the distance between two opposing boundary locations of the photoelectric conversion control circuit 401. Alternatively, the curvature, position, and inclination of the second concave reflector 302 can be determined stepwise according to a preset adjustment strategy until the transmitted light corresponding to the incident light at the positive principal ray angle at the boundary location of the photoelectric conversion control circuit 401 is reflected to the boundary region of the photosensitive unit 101 away from the photoelectric conversion control circuit 401. The specific process for iteratively determining the curvature, position, and inclination of the second concave reflector 302 can be referred to the aforementioned iterative process for the first concave reflector 301 and will not be further described here.

[0057] It should be noted that since the location of the first concave reflecting mirror 301 is related to the reflective light path of the second concave reflecting mirror 302, it is necessary to first determine the position, curvature, and inclination of the second concave reflecting mirror 302 through a step-by-step iterative process, so that the second concave reflecting mirror 302 satisfies the requirements of reflecting light to the photosensitive unit 101, maintaining the shortest vertical distance from the photoelectric conversion control circuit 401, and avoiding interference. After the position, curvature, and inclination of the second concave reflecting mirror 302 are determined, since the first concave reflecting mirror 301 requires the shortest possible optical path, the first concave reflecting mirror 301 and the second concave reflecting mirror 302 are connected, i.e., the position of the first concave reflecting mirror 301 is determined. The curvature of the first concave reflecting mirror 301 is then gradually and iteratively adjusted, so that the first concave reflecting mirror 301 meets the requirements of reflecting light to the photosensitive unit 101 without causing interference.

[0058] In some embodiments, the difference between the optical path of the light reflected to the photosensitive unit 101 and the optical path of the corresponding incident light is an integer multiple of the wavelength of the incident light.

[0059] To prevent interference between the reflected light and the incident light, which could lead to a reduction in light energy, the reflective unit 30 is configured so that the difference between the optical path length of the light reflected to the photosensitive unit 101 and the corresponding optical path length of the incident light is an integer multiple of the wavelength of the incident light. This ensures that interference does not occur and prevents light energy from dissipating. If the reflective unit 30 includes a first concave reflector 301 and a second concave reflector 302, the curvature and position of the first concave reflector 301, and the curvature, position, and inclination of the second concave reflector 302, must ensure that the optical path length difference is an integer multiple of the incident light.

[0060] In some embodiments, the curvature and position of the first concave reflecting mirror 301 are set to be within a first wavelength range, such that the offset between the actual focal point of incident light of each wavelength and the theoretical focal point of the central wavelength in the first wavelength range is less than or equal to an offset threshold; the curvature, position, and inclination of the second concave reflecting mirror 302 are set to be within a second wavelength range, such that the offset between the actual focal point of incident light of each wavelength and the theoretical focal point of the central wavelength in the second wavelength range is less than or equal to an offset threshold. The first wavelength range and the second wavelength range may not overlap, or may partially overlap, for example, the first wavelength range is the visible light band (400nm-700nm) and the second wavelength range is the near-infrared band (700nm-1700nm). The actual focus refers to the point where reflected light actually focuses. The theoretical focus refers to the geometric point where a concave reflector (or lens) converges parallel incident light rays under an ideal optical model. Its position is determined by the reflector's geometry and curvature and serves as the benchmark reference point for optical system design. The center wavelength refers to the wavelength at the midpoint within a range. For example, if the first wavelength range is 400nm-700nm, the center wavelength is 550nm.

[0061] When light passes through the photosensitive module 40 (e.g., silicon dioxide or silicon nitride), its refractive index varies with wavelength. Short wavelengths (e.g., 300nm ultraviolet) have a higher refractive index, while long wavelengths (e.g., 1700nm infrared) have a lower refractive index. This causes the focal position of light of different wavelengths to shift at the same curvature. As the curvature increases, the focal length decreases, the light convergence capability increases, and the depth of focus (the vertical range within which light remains sharply focused near the focal point) becomes shallower.

[0062] Therefore, to ensure that the reflected light corresponding to incident light of different wavelengths can be captured by the photosensitive unit 101, the curvature and position of the first concave reflector 301 are set to ensure that the offset between the actual focus of each wavelength and the theoretical focus of the center wavelength in the first wavelength range is less than or equal to an offset threshold within the first wavelength range. Specifically, based on the theoretical focus of the center wavelength of the first wavelength range (e.g., 550 nm), the actual focus of any wavelength within the wavelength range is ensured to meet the following requirements: the lateral offset (XY plane) is less than the lateral offset threshold (e.g., 10% of the side length of the photosensitive unit 101), and the longitudinal offset (Z axis) is less than the longitudinal offset (e.g., the thickness of the photosensitive unit 101). Limiting the lateral offset between the actual focus of different wavelengths and the theoretical focus of the center wavelength is intended to ensure that reflected light of different wavelengths in the first wavelength range is reflected to the first concave reflector 301. Limiting the longitudinal offset between the actual focus of different wavelengths and the theoretical focus of the center wavelength is intended to ensure that the focal points of reflected light of different wavelengths in the first wavelength range are located vertically within the photosensitive unit 101, ensuring that the reflected light can be clearly focused. In the second wavelength range, the offset between the actual focus of each wavelength of the second concave reflecting mirror 302 and the theoretical focus of the central wavelength in the second wavelength range is less than or equal to the offset threshold. The specific principle is the same as that of the first concave reflecting mirror 301 and will not be repeated here.

[0063] In some embodiments, according to the nonlinear mapping relationship between the curvature and position of the first concave reflecting mirror 301 and the curvature, position and inclination of the second concave reflecting mirror 302 and the effective light receiving efficiency, the curvature and position of the first concave reflecting mirror 301 and the curvature, position and inclination of the second concave reflecting mirror 302 are adjusted until the effective light receiving efficiency of the photosensitive unit 101 meets the desired threshold.

[0064] In some implementations, a neural network model is used to determine the curvature and position of the first concave reflector 301, as well as the curvature, position, and tilt angle of the second concave reflector 302, corresponding to the effective light receiving efficiency. The neural network model is trained to learn the aforementioned nonlinear mapping relationship. Specifically, a training data set is generated by randomly generating the curvature and three-dimensional coordinates of the first concave reflector 301, and the curvature, three-dimensional coordinates, and tilt angle of the second concave reflector 302 within a reasonable range (achievable by the optical structure). For each set of parameters, the corresponding effective light receiving efficiency is calculated using ray tracing simulation software. Random sampling is then used to generate a training set. Each training data item includes: input data: effective light receiving efficiency (a numerical value ranging from 0% to 100%); output data: curvature, three-dimensional coordinates, and tilt angle of the first concave reflector 301, and curvature, three-dimensional coordinates, and tilt angle of the second concave reflector 302. Construct the model neural network structure (inverse prediction model), input layer: 1 node (normalized target effective light receiving efficiency value), hidden layer, multiple fully connected layers (512-1024 neurons per layer), add residual connection (ResNet structure) to prevent gradient disappearance, activation function: ReLU is used in the first few layers, and Tanh is used in the last layer to constrain the output range, output layer: 5 nodes (corresponding to 5 optical parameters to be predicted), post-processing layer, impose physical constraints on the output parameters (such as curvature cannot be negative, inclination angle does not exceed ±45 degrees, etc.). The model is trained using a loss function consisting of a main loss, the mean squared error between the predicted and true parameters, and an auxiliary loss. The predicted parameters' effective light reception efficiency (ERE) error is verified using a fast forward model. During the coarse training phase, 80% of the data is used for training, with a batch size of 256 and a learning rate of 1e-3 for approximately 500 epochs. During the fine training phase, the full data is used for fine-tuning, with a batch size of 64 and a learning rate of 1e-5 for approximately 200 epochs. An early stopping mechanism is implemented, terminating the model if the validation set loss does not decrease after 10 consecutive epochs. The model meets the following criteria: the average error of the predicted parameters on the validation set is less than a preset threshold (e.g., curvature error less than 0.5% and position error less than 0.1 μm). Furthermore, the error between the predicted ERE of the five optical parameters and the target value after simulation is less than the error threshold. Using the trained model, the desired ERE is input (e.g., 0.85 represents 85%), and the model outputs five parameter values ​​that can be directly used for optical system adjustment.

[0065] In other implementations, the curvature and position of the first concave reflecting mirror 301, and the curvature, position, and inclination of the second concave reflecting mirror 302, corresponding to the effective light receiving efficiency, are determined through stepwise iteration. After the final desired effective light receiving efficiency is determined, the curvature and position of the first concave reflecting mirror 301, and the curvature, position, and inclination of the second concave reflecting mirror 302 are adjusted according to the priority of adjustment. For example, if it is necessary to first determine the parameters of the second concave reflecting mirror 302, after the position of the second concave reflecting mirror 302 is determined, the first concave reflecting mirror 301 is connected to it, and thus the position of the first concave reflecting mirror 301 is also determined, the curvature of the first concave reflecting mirror 301 is finally determined. The specific adjustment process is explained by taking the parameter adjustment of the second concave reflecting mirror 302 as an example. First, a fast scan is performed with a large step size, and then a fine step size local optimization is used in the optimal area. When m (an integer greater than 1) consecutive adjustments in the same direction are valid, the step size is automatically increased by a preset value. After the first adjustment fails, a binary reverse search is enabled instead of a simple reverse step. At the same time, three groups of parameter states (current optimal / forward exploration / reverse exploration) are maintained. After completing 5 iterations, the optimal branch is selected to continue. After completing each parameter optimization stage, the full parameter state is automatically saved. Finally, the historical optimal solution is selected instead of the last iteration result until the effective reception efficiency reaches the expected value.

[0066] In other feasible embodiments, since an optimal solution exists in the nonlinear mapping relationship for light within a bandwidth after the wavelength range is determined, the optimal solution can be found through the above-mentioned step-by-step iterative method. That is, when the curvature and position of the first concave reflecting mirror 301, and the curvature, position, and inclination of the second concave reflecting mirror 302 are fixed in a certain combination, the effective light receiving efficiency reaches a maximum, and the maximum value is found by step-by-step adjustment.

[0067] The image sensor disclosed herein utilizes a reflective unit 30 to recycle light that escapes into non-photosensitive areas. This dual-path mechanism of direct reception and reflective recycling extends the light capture range of the photosensitive unit 101 beyond the physical area limitations. The first concave reflector 301, based on a central wavelength (e.g., 550 nm), constrains lateral deviation (in the XY plane) and longitudinal focal depth (in the Z axis), ensuring that light between 400 and 700 nm is focused within the active area of ​​the photosensitive unit 101. The second concave reflector 302 compensates for lateral dispersion through tilt, and its low curvature design extends the focal depth, covering longitudinal deviations between 700 and 1700 nm. The optical path difference between the reflected and incident light is an integer multiple of the wavelength, minimizing energy loss caused by interference and ensuring multi-band signal integrity. The reflective unit 30 is strictly aligned with the orthographic projection of the photosensitive unit 101 or the photoelectric conversion control circuit 401, eliminating optical crosstalk between adjacent pixels. The reflective unit 30 is integrated on the backlight side of the readout circuit 102, making it compatible with conventional back-illuminated sensor processes without requiring modifications to the wafer-level packaging structure. The first concave reflector 301 captures incident light at the principal ray angle (positive and negative critical angles) at the edge of the photosensitive cell 101 and reflects it toward the center. The second concave reflector 302 directionally recovers transmitted light from the photoelectric control circuit area and reflects it toward the edge of the photosensitive cell 101, expanding the effective light-sensing range. A longitudinal offset threshold control ensures that the focal points of different wavelengths cover the entire thickness of the photosensitive layer, reducing light energy leakage in low illumination conditions.

[0068] The present disclosure also provides an imaging module, which includes an image processing unit and the image sensor shown in the above embodiments; the image processing unit is used to generate image data based on the digital signal output by the image sensor.

[0069] The present disclosure also provides an electronic device, which includes the above-mentioned imaging module.

[0070] It should be understood that the photosensitive module and electronic device provided by the present disclosure can implement the various processes of the above-mentioned image sensor embodiments and achieve the same technical effects. To avoid repetition, they will not be described here.

[0071] It should be noted that the technical solutions described in this disclosure can be combined arbitrarily without conflict.

[0072] The above description is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the present disclosure, and they should all be covered by the protection scope of the present disclosure.

Claims

1. An image sensor, characterized in that: The image sensor includes a plurality of photosensitive modules arranged in an array and a reflective unit corresponding to the photosensitive modules one by one, wherein the photosensitive module includes a photosensitive unit and a readout circuit; The reflecting unit is spaced apart from the readout circuit and is configured to reflect at least a portion of the light transmitted from the readout circuit to the photosensitive unit, so as to enhance the effective light receiving efficiency of the photosensitive unit.

2. The image sensor according to claim 1, wherein The reflection unit is configured to reflect the light transmitted by the readout circuit, the light that is not less than a preset ratio threshold, to the photosensitive unit.

3. The image sensor according to claim 1 or 2, characterized in that The reflecting unit comprises: At least one concave reflecting mirror is arranged to be a preset distance away from the readout circuit in a vertical direction perpendicular to the photosensitive surface of the photosensitive unit.

4. The image sensor according to claim 3, wherein: The readout circuit includes a photoelectric conversion control circuit and a peripheral circuit. The photoelectric conversion control circuit and the photosensitive unit are arranged in parallel on the same plane and are both arranged on one side of the peripheral circuit. The reflecting unit includes a first concave reflecting mirror and a second concave reflecting mirror. The first concave reflecting mirror is located on the backlight surface of the peripheral circuit and is located within the orthographic projection of the photosensitive unit in the vertical direction. The second concave reflecting mirror is located on the backlight surface of the peripheral circuit and is located within the orthographic projection of the photoelectric conversion control circuit in the vertical direction.

5. The image sensor according to claim 4, wherein: The first concave reflecting mirror and the second concave reflecting mirror are spaced apart from the peripheral circuit in the vertical direction, and the first concave reflecting mirror coincides with the projection of the photosensitive unit in the vertical direction, and the second concave reflecting mirror coincides with the projection of the photoelectric conversion control circuit in the vertical direction.

6. The image sensor according to claim 5, wherein: The curvature and position of the first concave reflector are set to: Reflecting the transmitted light corresponding to the incident light with a negative principal ray angle at a boundary position of the photosensitive unit away from the photoelectric conversion control circuit, and the transmitted light corresponding to the incident light with a positive principal ray angle at a boundary position close to the photoelectric conversion control circuit, to the central area of ​​the photosensitive unit; The positive chief ray angle is a critical angle at which the incident light is deflected clockwise relative to the vertical direction, and the negative chief ray angle is a critical angle at which the incident light is deflected counterclockwise relative to the vertical direction.

7. The image sensor according to claim 6, wherein: The first concave reflecting mirror is arranged outside the reflecting light path of the second concave reflecting mirror.

8. The image sensor according to claim 7, wherein: The first concave reflecting mirror is connected to the second concave reflecting mirror.

9. The image sensor according to claim 5, wherein The curvature, inclination and position of the second concave reflecting mirror are set to: Reflecting the transmitted light corresponding to the incident light at the positive principal ray angle at the boundary position of the photoelectric conversion control circuit away from the photosensitive unit to the boundary area of ​​the photosensitive unit away from the photoelectric conversion control circuit; and The second concave reflecting mirror is positioned at the shortest vertical distance from the photoelectric conversion control circuit, and the forward principal ray angle is a critical angle at which the incident light is deflected clockwise relative to the vertical direction.

10. The image sensor according to claim 5, wherein: The difference between the optical path of the light reflected to the photosensitive unit and the optical path of the corresponding incident light is an integer multiple of the wavelength of the incident light.

11. The image sensor according to any one of claims 4 to 10, characterized in that: The curvature and position of the first concave reflector are set to: In the first wavelength range, the offset between the actual focus of the reflected light of each wavelength and the theoretical focus of the central wavelength in the first wavelength range is less than or equal to the offset threshold; The curvature, position and inclination of the second concave reflecting mirror are set to: In the second wavelength range, the offset between the actual focus of each wavelength and the theoretical focus of the central wavelength in the second wavelength range is less than or equal to the offset threshold.

12. The image sensor according to any one of claims 4 to 10, characterized in that: According to the nonlinear mapping relationship between the curvature and position of the first concave reflecting mirror, the curvature, position and inclination of the second concave reflecting mirror and the effective light receiving efficiency, the curvature and position of the first concave reflecting mirror, and the curvature, position and inclination of the second concave reflecting mirror are adjusted until the effective light receiving efficiency of the photosensitive unit meets the expected threshold.

13. An imaging module, characterized in that: The photosensitive module comprises: an image processing unit and the image sensor according to any one of claims 1 to 12; The image processing unit is configured to generate image data based on the digital signal output by the image sensor.

14. An electronic device, characterized in that: The electronic device includes the imaging module according to claim 13.

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