Image sensor, camera module and electronic equipment

Abstract

The invention discloses an image sensor, a camera module and electronic equipment, and belongs to the technical field of photoelectricity. The image sensor comprises a pixel array, the pixel array comprises M rows of pixel modules and N columns of pixel modules, and M and N are positive integers; wherein each pixel module comprises a first pixel unit and a second pixel unit, and the first pixel unit is arranged around the second pixel unit; the first pixel unit comprises four first pixels, the four first pixels are arranged according to a 2 * 2 pixel arrangement mode, and the four first pixels comprise a red pixel, two green pixels and a blue pixel; the second pixel unit comprises four second pixels, and the four second pixels are arranged according to a 2 * 2 pixel arrangement mode; the cross-sectional area of the first pixel is larger than the cross-sectional area of the second pixel.

Description

Technical Field

[0001] This application belongs to the field of optoelectronic technology, and particularly relates to an image sensor, a camera module, and an electronic device. Background Art

[0002] At present, in the mobile terminal products, the market competition is becoming increasingly fierce, especially in the aspect of smartphone photography. The competition among various terminals is extremely fierce, mainly reflected in the improvement of the image quality signal-to-noise ratio and dynamic range.

[0003] The dynamic range of the real world is very high, often up to 300 dB. The dynamic range of the human eye is approximately between 100 dB and 180 dB. However, the dynamic range of a conventional Complementary Metal-Oxide-Semiconductor (CMOS) image sensor (CIS) is only about 60 dB. In order to make the photos taken by the CIS camera more realistic and closer to what the human eye sees, it is necessary to improve the light-sensing ability of the CIS for dark scenes, improve the signal-to-noise ratio, and for bright areas, the CIS needs to have a high dynamic range ability.

[0004] Currently, the CIS cannot have both of these two abilities in one frame and can only switch the output, that is, multi-frame bracketed exposure, or output 2 frames in one exposure, that is, the Dual Conversion Gain (DCG) High-Dynamic Range (HDR) mode, and then perform post-processing fusion or synthesis; both of these two methods can effectively improve the dynamic range of camera photography. However, currently, the DCG HDR technology has a poor effect on expanding the dynamic range of images, thus affecting the photography effect.

[0005] In addition, to improve the dynamic range, a variable aperture is also a method. By freely controlling the size of the aperture opening, the amount of incident light can be controlled. The aperture is reduced in high-light scenes to reduce the amount of incident light and prevent overexposure; the aperture is enlarged in dark environments such as night scenes to increase the amount of incident light and improve the signal-to-noise ratio. However, the variable aperture will bring problems of poor photography effect. Summary of the Invention

[0006] The purpose of the embodiments of this application is to provide an image sensor, a camera module, and an electronic device to solve the problems of limited dynamic range and poor photography effect of the existing image sensor.

[0007] To solve the above problems, in the first aspect, the embodiments of this application provide an image sensor, including:

[0008] A pixel array, the pixel array includes M rows of pixel modules and N columns of pixel modules, where M and N are positive integers;

[0009] Among them, each of the pixel modules includes a first pixel unit and a second pixel unit, and the first pixel unit is disposed around the second pixel unit;

[0010] The first pixel unit includes four first pixels, the four first pixels are arranged in a 2×2 pixel arrangement, and the four first pixels include one red pixel, two green pixels, and one blue pixel;

[0011] The second pixel unit includes four second pixels, and the four second pixels are arranged in a 2×2 pixel arrangement;

[0012] The cross-sectional area of the first pixel is larger than the cross-sectional area of the second pixel.

[0013] In some embodiments, the four second pixels have the same color.

[0014] In some embodiments, the first pixel includes a first photodiode, a first filter, and a first microlens that are sequentially stacked;

[0015] The second pixel includes a second photodiode and a second filter that are sequentially stacked. The four second pixels correspond to one second microlens, and the second microlens is disposed on a side of the second filter away from the second photodiode.

[0016] In some embodiments, the image sensor further includes: a first transfer switch transistor, a second transfer switch transistor, and a first capacitor;

[0017] Among them, the positive electrode of the first photodiode is grounded and the negative electrode is connected to the source electrode of the first transfer switch transistor;

[0018] The drain electrode of the first transfer switch transistor is connected to the signal terminal;

[0019] The positive electrode of the second photodiode is grounded and the negative electrode is connected to the source electrode of the second transfer switch transistor;

[0020] The drain electrode of the second transfer switch transistor is connected to the signal terminal;

[0021] One end of the first capacitor is grounded and the other end is connected to the signal terminal.

[0022] In some embodiments, the image sensor further includes: at least one second capacitor;

[0023] Among them, in the case where the at least one second capacitor includes one second capacitor, one end of the second capacitor is grounded and the other end is connected to the signal terminal;

[0024] In the case where the at least one second capacitor includes at least two second capacitors, the at least two second capacitors are arranged in parallel, and one end of each second capacitor among the at least two second capacitors is grounded and the other end is connected to the signal terminal.

[0025] In some embodiments, the capacitance of the second capacitor is 10 to 100 times that of the first capacitor.

[0026] In some embodiments, each of the capacitors is a lateral overflow integrating capacitor.

[0027] In some embodiments, the image sensor further includes: at least one capacitor control switch; each capacitor control switch is connected to a capacitor.

[0028] In some embodiments, the image sensor further includes: a reset transistor, a source follower, and a selection transistor;

[0029] The drain of the reset transistor is connected to the power supply terminal, the source of the reset transistor is connected to the signal terminal, the gate of the source follower is connected to the signal terminal, the drain of the source follower is connected to the power supply terminal, the drain of the selection transistor is connected to the source of the source follower, and the source of the selection transistor is connected to the output signal line.

[0030] In a second aspect, an embodiment of the present application further provides an imaging module, including:

[0031] A circuit board;

[0032] An image sensor, the image sensor is electrically connected to the circuit board, and the image sensor is the image sensor described in the first aspect above; and,

[0033] A lens, the lens is disposed on a side of the image sensor away from the circuit board.

[0034] In a third aspect, an embodiment of the present application further provides an electronic device, including the imaging module described in the second aspect above.

[0035] In the embodiment of the present application, a pixel module is designed, which includes a first pixel unit and a second pixel unit, and the first pixel unit is arranged around the second pixel unit. Among them, the first pixel unit includes four first pixels arranged in a 2×2 pixel arrangement pattern, and the four first pixels include one red pixel, two green pixels, and one blue pixel; the second pixel unit includes four second pixels arranged in a 2×2 pixel arrangement pattern. The cross-sectional area of the first pixel is larger than that of the second pixel. Based on the above pixel module, an image sensor can be expanded, which can provide an ultra-large dynamic range. The large pixel (the first pixel) has strong photosensitive ability, and in the extreme night environment, the camera can obtain better picture quality and less noise through the large pixel. The small pixel (the second pixel) has weak photosensitive ability, and in the high-brightness environment, the high dynamic range can be obtained through the small pixel. The small pixel also supports phase focusing, which is beneficial to the rapid focusing in scenarios such as space, bringing a better photo-taking effect and user experience to users. Description of the Drawings

[0036] Figure 1 is a schematic structural diagram of the camera module;

[0037] Figure 2 is a schematic diagram of the pixel filter array corresponding to the Bayer format in the related art;

[0038] Figure 3 is a schematic diagram of the pixel filter array corresponding to the four-in-one format in the related art;

[0039] Figure 4 is a schematic diagram of the pixel filter array corresponding to the 16-in-one format in the related art;

[0040] Figure 5 is a schematic diagram of the pixel circuit of the image sensor in the related art;

[0041] Figure 6 is a schematic structural diagram of the image sensor according to the embodiment of the present application;

[0042] Figure 7 is a schematic structural diagram of the pixel module according to the embodiment of the present application;

[0043] Figure 8 is one of the cross-sectional views of the pixel module according to the embodiment of the present application;

[0044] Figure 9 is the second cross-sectional view of the pixel module according to the embodiment of the present application;

[0045] Figure 10 is a schematic diagram of the pixel circuit of the image sensor according to the embodiment of the present application;

[0046] Figure 11 is a schematic diagram of the photo effect obtained when the photosensitivity is overexposed;

[0047] Figure 12 It is a schematic diagram of the photo effect obtained when the photosensitivity is normal. Specific embodiments

[0048] Next, the technical solutions in the embodiments of the present application will be clearly described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0049] The terms "first", "second", etc. in the specification of the present application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are usually of the same type, and the number of objects is not limited. For example, the first object can be one or multiple. In addition, "and / or" in the specification means at least one of the connected objects, and the character " / " generally means an "or" relationship between the associated objects before and after.

[0050] To facilitate understanding of the solution of the present application, the relevant content involved in the present application will be introduced first.

[0051] The image sensor is the core of a camera and also the most crucial source of data information for imaging. Image sensors are mainly divided into two types. One is the widely used charge-coupled device (CCD); the other is the CMOS image sensor (CIS). Compared with traditional cameras, traditional cameras use "film" as the carrier for recording information, while the "film" of digital cameras is their imaging photosensitive element. The photosensitive element is the "film" that does not need to be replaced in a digital camera and is integrated with the camera.

[0052] Currently, the mainstream is the CMOS image sensor. It, like the CCD, is a semiconductor that can record light changes in a digital camera. The CMOS image sensor is mainly a device made of silicon material using semiconductor manufacturing process technology. N-type (negatively charged) and P-type (positively charged) photodiodes are formed by ion implantation to absorb photoelectrons. The photoelectrons are converted into voltage signals through a circuit and can be recorded and interpreted into images by a subsequent signal processing chip.

[0053] See Figure 1, in a conventional camera (imaging) module, the lens group 201 is used for light collection and focusing. The lens group 201 is wrapped and fixed by the voice coil motor 202, and the upper and lower ends of the voice coil motor 202 are connected to the shrapnel. During focusing, an electric current is applied to make the voice coil motor 202 generate an electromagnetic force, which ultimately balances with the elastic force of the shrapnel. The position of the voice coil motor 202 can be controlled by the magnitude of the applied current, thereby pushing the voice coil motor 202 and the lens group 201 to the in-focus position.

[0054] The scene light converging into the camera module is projected onto the infrared filter 203. The function of the infrared filter 203 is to filter out unnecessary infrared light projected onto the image sensor 204, prevent the image sensor 204 from generating false colors / ripples, and improve its effective resolution and color reproducibility. The light passing through the infrared filter 203 can be sensed by the image sensor 204.

[0055] The arrangement of the color filter array of the image sensor 204 in this camera module can be in the Bayer format or in a multi-in-one format, such as four-in-one, nine-in-one, sixteen-in-one, etc. Among them, the pixel filter array corresponding to the Bayer format is as Figure 2 shown, the pixel filter array corresponding to the four-in-one format is as Figure 3 shown, and the pixel filter array corresponding to the sixteen-in-one format is as Figure 4 shown.

[0056] See Figure 5 , which is the pixel circuit of the image sensor in a conventional camera module. This pixel structure is called the pixel structure of the PPD structure (Pinned Photodiode Pixel). The PPD pixel includes a photosensitive region PD1, that is, a photosensitive diode, and four transistors (a reset triode RST, a floating switch TX1, a row selector SET, and a signal amplifier SF), so it is also called a 4T pixel structure. The PPD allows the introduction of a correlated double sampling (CDS) circuit, eliminating the kTC noise introduced by reset, the 1 / f noise and offset noise introduced by MOS transistors. The specific working mode of this pixel circuit is as follows:

[0057] 1. Exposure: RST and TX1 are opened simultaneously to clear the residual electrons in PD1. Then both are disconnected, and exposure starts. The electron-hole pairs generated by light irradiation will be separated due to the existence of the PD1 electric field. Electrons move to the n region, and holes move to the p region.

[0058] 2. Reset: At the end of exposure, RST is activated to reset FD1 to a high level.

[0059] 3. Reset level readout: After reset is completed, the reset level of FD1 is read out, which includes the offset noise, 1 / f noise of the MOS transistor, and the kTC noise introduced by reset. The read signal is stored in the first capacitor (not shown in the figure).

[0060] 4. Charge transfer: Activate TX to completely transfer the charge from the photosensitive area to FD1 for readout. The mechanism here is similar to the charge transfer in CCDs.

[0061] 5. Signal level readout: The voltage signal of FD1 is read out to the second capacitor (not shown in the figure). The signals here include the signals generated by photoelectric conversion, the offset generated by the operational amplifier, 1 / f noise, and the kTC noise introduced by reset.

[0062] 6. Signal output: Subtract the signals stored in the two capacitors (if CDS is used, the main noise in the pixel can be eliminated). The obtained signal is then amplified analogously and then sampled by the analog-to-digital conversion ADC module to enable digital signal output.

[0063] The dynamic range (DR), also known as the exposure range, refers to the range of light intensities captured by a camera. It is usually expressed in f-Stops, exposure values (EV), or zones (exposure range).

[0064] The dynamic range was originally a concept used to describe signal systems. For image signals, it is the ratio of the maximum value to the minimum value of the variable light signal. In photography, the dynamic range is also called the latitude. Generally speaking, the dynamic range is used to describe the range of light intensity distribution from the darkest shadow part to the brightest highlight part in a picture. Usually, it is expressed in decibels (dB), and can also be expressed in bits or stops.

[0065] The larger the dynamic range, the richer the levels that can be represented in the image, and the wider the color space it contains.

[0066] HDR is the abbreviation of High-Dynamic Range, referring to the range between the brightest and darkest lights that can be seen in a photo. The dynamic range we can see with the naked eye is much larger than that of a camera, and we can easily see the details of dark objects under a bright sky. Now mobile phone cameras also support the HDR mode, that is, the high-dynamic range mode. After enabling the HDR mode on a mobile phone camera, the brightness range of the picture can be improved, so that the highlights are not overexposed, the dark tones are not underexposed, and more details are presented in the dark areas.

[0067] Currently, mainstream HDR uses a multi-exposure and multi-frame fusion method to achieve a high dynamic range of the image. However, the multi-exposure and multi-frame fusion method will produce motion blur (Motion Blur) for the moving objects captured. A complex deblurring algorithm must be superimposed subsequently, and short-exposure frames are used as reference frames for moving objects for moving object recognition, object segmentation, and deblurring. In addition, long-exposure frames are used to extract details in low-light areas. This method will have worse imaging effects for moving objects captured in low-light scenes. Currently, the time ratio of long to short exposure is generally 1:16. Although a too large exposure ratio will result in a higher dynamic range, it will cause discontinuity in the signal after multi-frame fusion, resulting in obvious image join lines.

[0068] In order to solve the problem of motion blur, DCG HDR technology was proposed. Under single exposure, the switching operation of pixel transistors is used to output two frames of high conversion gain (HCG) and low conversion gain (LCG). HCG has better readout noise and LCG has greater charge reading capability, which can avoid signal saturation in highlight areas. The fusion of HCG and LCG images can achieve a single-exposure high dynamic range image. Because it is a single exposure, it has better de-motion blur capability for moving objects in the scene.

[0069] However, due to the structural relationship of the pixels themselves, the HCG:LCG of DCG HDR is generally about 1:2 or 1:4. Too small a gain ratio will not be effective in expanding the dynamic range of the image, thus affecting the photo effect.

[0070] Variable aperture can also improve the dynamic range of the camera, but it also has disadvantages. First, the variable aperture will lead to a decline in the optical quality of the entire camera module, and more optical defects in photos, such as flare, halo ghost, local blur, etc. In addition, the drive motor of the variable aperture is relatively large, with high power consumption and current, which will cause heat, electromagnetic interference, etc., affecting the working environment of the image sensor, and thus resulting in a decline in the photo effect.

[0071] In order to solve the above technical problems, an embodiment of the present application provides an image sensor. The image sensor provided by the embodiment of the present application is described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0072] like Figures 6 to 10, the image sensor according to the embodiment of the present application includes: a pixel array 100, the pixel array 100 includes M rows of pixel modules 101 and N columns of pixel modules 101, where M and N are integers; wherein, each pixel module 101 includes a first pixel unit 1 and a second pixel unit 2, and the first pixel unit 1 is arranged around the second pixel unit 2.

[0073] The first pixel unit 1 includes four first pixels (11, 12, 13, 14), and the four first pixels (11, 12, 13, 14) are arranged in a 2×2 pixel arrangement, and the four first pixels (11, 12, 13, 14) include one red pixel R, two green pixels (Gr, Gb), and one blue pixel B.

[0074] It should be understood that the four first pixels (11, 12, 13, 14) being arranged in a 2×2 pixel arrangement means that the four first pixels (11, 12, 13, 14) are arranged in two rows and two columns.

[0075] The four first pixels (11, 12, 13, 14) including one red pixel R, two green pixels (Gr, Gb), and one blue pixel B can also be understood as that the arrangement sequence (i.e., the filter sequence) of the color filters covering the photodiodes of the first pixels is RGrGbB, where R represents a red color filter, Gr represents a green color filter, Gb represents a green color filter, and B represents a blue color filter. That is, the four first pixels (11, 12, 13, 14) correspond to a filtering pattern of Bayer pattern, and the sequence is RGGB.

[0076] The second pixel unit 2 includes four second pixels (21, 22, 23, 24), and the four second pixels (21, 22, 23, 24) are arranged in a 2×2 pixel arrangement; wherein, the cross-sectional area of the first pixel (11, 12, 13 or 14) is larger than the cross-sectional area of the second pixel (21, 22, 23, 24).

[0077] Optionally, the cross-sectional area of the first pixel (11, 12, 13, 14) is K 2 times that of the cross-sectional area of the second pixel (21, 22, 23 or 24), and K is an integer greater than 1.

[0078] It should be understood that the four second pixels (21, 22, 23, 24) being arranged in a 2×2 pixel arrangement means that the four second pixels (21, 22, 23, 24) are arranged in two rows and two columns. It should be noted that the color filters covering the photodiodes of the second pixels (21, 22, 23, 24) are color filters or full-wave filters.

[0079] The cross-sectional area of the first pixels (11, 12, 13, 14) is larger than that of the second pixels (21, 22, 23, 24), indicating that the first pixels are large pixels and the second pixels are small pixels.

[0080] The image sensor according to the embodiment of the present application is a sensor expanded based on the above pixel module and belongs to a hybrid color arrangement array. The large pixels (the first pixels) have strong photosensitive ability and are mainly used to improve the signal-to-noise ratio in dark scenes (such as grasslands, tree shades, etc.); the small pixels have weak photosensitive ability, and then cooperate with the lateral overflow integration capacitor lofic structure, with stronger dynamic range ability and supporting phase detection autofocus (Phase Detection Auto Focus, PDAF), and are mainly used to see more details and focus quickly in bright scenes (such as the sun and clouds, etc.).

[0081] Optionally, the four second pixels (21, 22, 23, 24) have the same color. This is beneficial for the image sensor to perform phase detection autofocus (Phase Detection Auto Focus, PDAF).

[0082] In some embodiments, the first pixels (11, 12, 13, 14) include a first photodiode PD_B, a first filter 3, and a first microlens 4 stacked in sequence. That is, the first photodiode PD_B is covered with the first filter 3 and the first microlens 4. Among them, the first microlens 4 is used to guide light into the first photodiode PD_B, and the first filter 3 filters the light, and only allows the light in the band corresponding to the color of the first filter 3 to pass through.

[0083] Here, the first filter 3 is a color filter. Different first pixels correspond to different first filters. The first filter 3 included in the first pixel 11 is a red filter, represented by R, the first filter 3 included in the first pixel 12 is a green filter, represented by Gr, the other first filter 3 included in the first pixel 13 is a green filter, represented by Gb, and the first filter 3 included in the first pixel 14 is a blue filter, represented by B. That is, the filtering sequence corresponding to the four first pixels (11, 12, 13, 14) is RGGB.

[0084] The second pixels (21, 22, 23, 24) include a second photodiode PD_S and a second filter 5 which are stacked in sequence. Four second pixels (21, 22, 23, 24) correspond to one second microlens 6. The second microlens 6 is disposed on a side of the second filter 5 facing away from the second photodiode PD_S. That is, the second photodiode PD_S is covered with the second filter 5 and the second microlens 6. Wherein, the second microlens 6 is used to guide light into the second photodiode PD_S, and the second filter 5 filters the light, allowing only the light in the wavelength band corresponding to the color of the second filter 5 to pass through.

[0085] As an optional embodiment, refer to Figure 10 , the image sensor of the present application further includes: a first transfer switch transistor TG2, a second transfer switch transistor TG1, and a first capacitor FD1; wherein, the positive electrode of the first photodiode PD_B is grounded and the negative electrode is connected to the source electrode of the first transfer switch transistor TG2; the drain electrode of the first transfer switch transistor TG2 is connected to the signal terminal Vs; the positive electrode of the second photodiode PD_S is grounded and the negative electrode is connected to the source electrode of the second transfer switch transistor TG1; the drain electrode of the second transfer switch transistor TG1 is connected to the signal terminal Vs; one end of the first capacitor FD1 is grounded and the other end is connected to the signal terminal Vs.

[0086] Wherein, the photodiodes (the first photodiode PD_B and the second photodiode PD_S) in the present application are used to receive the optical signal from the external environment and enter the image sensor via the lens and the infrared filter. The photodiode is a semiconductor mainly made of two elements, silicon and germanium, on which there coexist semiconductors with N-level (negatively charged) and P-level (positively charged). The current generated by their complementary effect can be recorded and interpreted by the processing chip. Thus, when the photodiode receives light, it will generate charges and convert the light into an electrical signal.

[0087] Furthermore, the image sensor of the present application further includes: a reset transistor RST1, a source follower SF1, and a selection transistor SET1; the drain electrode of the reset transistor RST1 is connected to the power supply terminal VDD, the source electrode of the reset transistor RST1 is connected to the signal terminal Vs, the gate electrode of the source follower SF1 is connected to the signal terminal Vs, the drain electrode of the source follower SF1 is connected to the power supply terminal VDD, the drain electrode of the selection transistor SET1 is connected to the source electrode of the source follower SF1, and the source electrode of the selection transistor SET1 is connected to the output signal line Vout.

[0088] In this embodiment, the drain electrode of the first transfer switch transistor TG2 is respectively connected to the source electrode of the reset transistor RST1 and the gate electrode of the source follower SF1.

[0089] The first transfer switch transistor TG2 is used to transfer the electrical signal from the first photodiode PD_B to the source follower SF1. The reset transistor RST1 can control the reset of the first capacitor FD1. The source follower SF1 can read out the electrical signal transferred via the first transfer switch transistor TG2.

[0090] One end of the first capacitor FD1 is grounded and the other end is connected to the drain of the first transfer switch transistor TG2, the source of the reset transistor RST1, and the gate of the source follower SF1.

[0091] It should be noted that for the case of charge transfer of PD_D, the reset transistor RST1 and the first transfer switch transistor TG2 need to be activated first to clear the residual electrons in the first photodiode PD_B and the first capacitor FD1. After clearing, RST1 and the first transfer switch transistor TG2 are disconnected, and then exposure starts. The electron-hole pairs generated by light irradiation will be separated due to the existence of the electric field of PD_B. The electrons move to the n region and the holes move to the p region. After an interval of exposure time, the first transfer switch transistor TG2 is activated, and then the charges generated by the first photodiode PD_B during the exposure period can be completely transferred from the photosensitive region to the first capacitor FD1 for reading. After the selection transistor SET1 is turned on, the photo-generated charges pass through the source follower SF1 from the first capacitor FD1 to output the voltage signal of the signal line Vout1.

[0092] Here, the first photodiode PD_B has strong photosensitivity and is mainly used to improve the signal-to-noise ratio in a dark scene. Through the above working process, better picture quality noise can be obtained in darker places in the environment.

[0093] In addition, the drain of the second transfer switch transistor TG1 is respectively connected to the source of the reset transistor RST1 and the gate of the source follower SF1.

[0094] The second transfer switch transistor TG1 is used to transfer the electrical signal from the second photodiode PD_S to the source follower SF1. The reset transistor RST1 can control the reset of the first capacitor FD1. The source follower SF1 can read out the electrical signal transferred via the second transfer switch transistor TG1.

[0095] One end of the first capacitor FD1 is grounded and the other end is connected to the drain of the second transfer switch transistor TG1, the source of the reset transistor RST1, and the gate of the source follower SF1.

[0096] It should be noted that for the case of PD_S charge transfer, the reset transistor RST1 and the second transfer switch transistor TG1 need to be activated first to clear the residual electrons in the second photodiode PD_S and the first capacitor FD1. After clearing, RST1 and the second transfer switch transistor TG1 are disconnected, and then exposure starts. The electron-hole pairs generated by light irradiation will be separated due to the existence of the PD_S electric field. Electrons move to the n region, and holes move to the p region. After an interval exposure time, the second transfer switch transistor TG1 is activated, and then the charges generated by the second photodiode PD_S during the exposure period can be completely transferred from the photosensitive region to the first capacitor FD1 for reading. Then, after the selection transistor SET1 is turned on, the photo-generated charges pass through the source follower SF1 from the first capacitor FD1, and are output as the voltage signal of the output signal line Vout2.

[0097] Here, the photosensitive ability of the second photodiode PD_S is weak. After cooperating with the lateral overflow integration capacitor lofic structure, the dynamic range ability is stronger, which is mainly used to see more details in bright scenes. In this way, through the above working process, more details can be obtained in brighter places in the environment, and rapid focusing can be achieved.

[0098] Furthermore, the image sensor of the present application further includes at least one second capacitor (Lofic1, Lofic2); wherein, when at least one second capacitor (Lofic1, Lofic2) includes one second capacitor (Lofic2), one end of the second capacitor (Lofic2) is grounded and the other end is connected to the signal terminal Vs; when at least one second capacitor (Lofic1, Lofic2) includes at least two second capacitors (Lofic1, Lofic2), at least two second capacitors (Lofic1, Lofic2) are arranged in parallel, and one end of each second capacitor in at least two second capacitors (Lofic1, Lofic2) is grounded and the other end is connected to the signal terminal Vs.

[0099] That is, when at least one second capacitor (Lofic1, Lofic2) includes one second capacitor Lofic2, one end of the second capacitor Lofic2 is grounded and the other end is connected to the drain of the second transfer switch transistor TG1, the source of the reset transistor RST1, and the gate of the source follower SF1;

[0100] When at least one second capacitor (Lofic1, Lofic2) includes at least two second capacitors (Lofic1, Lofic2), the at least two second capacitors (Lofic1, Lofic2) are arranged in parallel, and one end of each of the at least two second capacitors (Lofic1, Lofic2) is grounded and the other end is connected to the drain of the second transfer switch transistor TG1, the source of the reset transistor RST1, and the gate of the source follower SF1.

[0101] Optionally, each second capacitor (Lofic1, Lofic2) is a lateral overflow integration capacitor.

[0102] Optionally, the capacitance of the second capacitor (Lofic1, Lofic2) is a positive integer multiple of the first capacitor FD1. It should be noted that the parasitic capacitance of the lateral overflow integration capacitor is very large, generally about 10 to 100 times that of the first capacitor FD1. This can expand the dynamic range of the pixel, approaching the brightness range perceivable by the human eye, and can greatly improve the camera's ability to take pictures of landscape scenes. At the same time, because the second photodiode PD_S has a four-in-one Qcell structure, in a high-brightness environment, the second photodiode PD_S can not only see details clearly, but also perform PDAF focusing on high-brightness objects.

[0103] Optionally, the image sensor of the present application further includes: at least one capacitor control switch (TG3, TG4); each capacitor control switch (TG3, TG4) is connected to a second capacitor (Lofic1, Lofic2). Here, the capacitor control switch is used to control the on / off of the second capacitor. When the first capacitor FD1 is saturated, the capacitor control switch is closed to turn on the second capacitor to store the charge transferred from the first capacitor FD1, thereby reducing the voltage of the output signal line and preventing overexposure of the photosensitive element.

[0104] Here, adding at least one second capacitor (Lofic1, Lofic2) is to share the charge filled in the first capacitor FD1, which will reduce the voltage of the output signal line and prevent overexposure of the photosensitive element. Among them, the photo effect obtained during overexposure of the photosensitive element is as Figure 11 shown; the photo effect obtained during normal photosensitivity is as Figure 12 shown.

[0105] In some embodiments, at least one second capacitor (Lofic1, Lofic2) includes a second capacitor Lofic2 and a second capacitor Lofic1 that are connected in parallel to each other and are respectively grounded; at least one capacitor control switch (TG3, TG4) includes a first capacitor control switch TG4 and a second capacitor control switch TG3. The first capacitor control switch TG4 is disposed between the first capacitor FD1 and the second capacitor Lofic2, and the second capacitor control switch TG3 is disposed between the second capacitor Lofic2 and the second capacitor Lofic1.

[0106] Since the parasitic capacitance of Lofic is very large, generally about 10 to 100 times that of FD1, assuming it is 100 times. If Lofic2 is 100 times FD1 and Lofic1 is 100 times Lofic2, the dynamic range of the pixels of the present application can exceed 140 dB (the conventional pixel is 60 dB, two stages of Lofic with 10,000 times is about 80 dB, a total of 140 dB). It is close to the brightness range that can be perceived by the human eye and can greatly improve the landscape scene photographing ability of the camera.

[0107] In some embodiments, the image sensor of the present application further includes: an analog-to-digital conversion ADC module, a signal processing module ISP, and a processor interface MIPI; the analog-to-digital conversion ADC module is connected to the output signal line Vout; the signal processing module ISP is respectively connected to the analog-to-digital conversion ADC module and the processor interface MIPI.

[0108] Among them, the output voltage Vout of the pixel is output to the ADC module to quantize the Vout voltage, and is output as a 10-bit digital signal value, that is, image data, and then is transmitted to the backend AP through the processor interface MIPI after being processed by the ISP.

[0109] See Figure 10 the pixel circuit shown, and the specific operation process of this pixel circuit is as follows:

[0110] 1. Pixel clearing.

[0111] First, activate RST1, TG1 to TG4 to clear the residual electrons in the first photodiode PD_B, the second photodiode PD_S, and the first capacitor FD1, the second capacitor Lofic2, and the second capacitor Lofic1. After clearing, disconnect RST1, TG1 to TG4, and start exposure. The electron-hole pairs generated by light irradiation will be separated due to the existence of the electric fields of the first photodiode PD_B and the second photodiode PD_S. Electrons move to the n region, and holes move to the p region.

[0112] 2. PD_B charge transfer.

[0113] Disconnect RST1. After an interval exposure time, activate the first transfer switch transistor TG2. Then, the charges generated by PD_B during the exposure period can be completely transferred from the photosensitive region to the first capacitor FD1 for reading. After opening the selection transistor SET1, the photo-generated charges pass through the source follower SF1 and are output as a voltage signal of Vout1.

[0114] 3. Charge transfer of PD_S.

[0115] Close RST1, TG3, and TG4 to clear the residual electrons in FD1, Lofic1, and Lofic2. Then, disconnect RST1, TG3, and TG4. After an interval exposure time, close the second transfer switch transistor TG1. Then, the charges generated by PD_S during the exposure period can be completely transferred from the photosensitive region to the first capacitor FD1 for reading. If the photographed scene is a high-brightness scene at this time and FD1 is saturated, then close TG4 and open the first-stage Lofic2 capacitor. If the photosensitivity is still overexposed, continue to close TG3 and open the second-stage Lofic1 capacitor. After opening the selection transistor SET1, the photo-generated charges pass through the source follower SF1 and are output as a voltage signal of Vout2.

[0116] The parasitic capacitance of Lofic is very large, generally about 10 to 100 times that of FD1. Assume it is 100 times. If Lofic2 is 100 times FD1 and Lofic1 is 100 times Lofic2, the dynamic range of the pixels in this application can exceed 140 dB (the conventional pixel is 60 dB, the two-stage Lofic of 10,000 times is about 80 dB, and the total is 140 dB). It is close to the brightness range that can be perceived by the human eye and can greatly improve the camera's ability to take pictures of landscape scenes.

[0117] 4. Signal processing.

[0118] The output voltage Vout of the pixel is output to the ADC module to quantize the Vout voltage, and the output is a 10-bit digital signal value, that is, the image data. After being processed by ISP, it is transmitted to the backend AP through MIPI.

[0119] The purpose of this application is to design a new type of COMS image sensor, which includes a new pixel structure and a pixel circuit. The pixel module of this application (i.e., the smallest unit of the image sensor) includes four large pixels (the first pixel) and four small pixels (the second pixel). The large pixel is of Bayer structure, and the small pixel is of four-in-one Qcell structure. The image sensor of this application can provide an ultra-large dynamic range. In the extremely dark environment, the camera can obtain better picture quality noise through the large pixel. In the high-brightness environment, the high dynamic range can be obtained through the small pixel. The small pixel also supports phase focusing, which is beneficial to the rapid focusing in scenes such as space, bringing a better photo-taking effect and user experience to users.

[0120] An embodiment of the present application further provides an imaging module, including: a circuit board; an image sensor, electrically connected to the circuit board, and the image sensor is the image sensor described in the above embodiment; and a lens, disposed on a side of the image sensor away from the circuit board.

[0121] An embodiment of the present application further provides an electronic device, including the imaging module described above.

[0122] It should be noted that the electronic device in the embodiment of the present application includes the above-mentioned mobile electronic device and non-mobile electronic device.

[0123] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the claims of the present application, and all of them belong to the protection scope of the present application.

Claims

1. An image sensor, characterized in that, Comprising: A pixel array, the pixel array comprising M rows of pixel modules and N columns of pixel modules, where M and N are positive integers; Wherein, each of the pixel modules includes a first pixel unit and a second pixel unit, and the first pixel unit is disposed around the second pixel unit; The first pixel unit includes four first pixels, the four first pixels are arranged in a 2×2 pixel arrangement, and the four first pixels include one red pixel, two green pixels, and one blue pixel; The second pixel unit includes four second pixels, the four second pixels are arranged in a 2×2 pixel arrangement; The cross-sectional area of the first pixel is larger than the cross-sectional area of the second pixel.

2. The image sensor according to claim 1, characterized in that, The four second pixels have the same color.

3. The image sensor according to claim 1, characterized in that, The first pixel includes a first photodiode, a first filter, and a first microlens stacked in sequence; The second pixel includes a second photodiode and a second filter stacked in sequence, the four second pixels correspond to one second microlens, and the second microlens is disposed on a side of the second filter away from the second photodiode.

4. The image sensor according to claim 3, wherein, Further comprising: A first transfer switch transistor, a second transfer switch transistor, and a first capacitor; Wherein, the positive electrode of the first photodiode is grounded and the negative electrode is connected to the source electrode of the first transfer switch transistor; The drain electrode of the first transfer switch transistor is connected to a signal terminal; The positive electrode of the second photodiode is grounded and the negative electrode is connected to the source electrode of the second transfer switch transistor; The drain electrode of the second transfer switch transistor is connected to a signal terminal; One end of the first capacitor is grounded and the other end is connected to the signal terminal.

5. The image sensor according to claim 4, wherein Further comprising: At least one second capacitor; Wherein, in the case that the at least one second capacitor includes one second capacitor, one end of the second capacitor is grounded and the other end is connected to the signal terminal; In the case that the at least one second capacitor includes at least two second capacitors, the at least two second capacitors are connected in parallel, and one end of each of the at least two second capacitors is grounded and the other end is connected to the signal terminal.

6. The image sensor according to claim 5, wherein, The capacitance of the second capacitor is 10 to 100 times that of the first capacitor.

7. The image sensor according to claim 5, characterized in that Each of the second capacitors is a lateral overflow integration capacitor.

8. The image sensor according to claim 5, wherein Further comprising: At least one capacitor control switch; Each of the capacitor control switches is connected to one of the second capacitors.

9. The image sensor according to claim 4, wherein, Further comprising: A reset transistor, a source follower, and a selection transistor; The drain electrode of the reset transistor is connected to a power supply terminal, the source electrode of the reset transistor is connected to the signal terminal, the gate electrode of the source follower is connected to the signal terminal, the drain electrode of the source follower is connected to the power supply terminal, the drain electrode of the selection transistor is connected to the source electrode of the source follower, and the source electrode of the selection transistor is connected to an output signal line.

10. An imaging module, characterized in that, Comprising: A circuit board; An image sensor, the image sensor is electrically connected to the circuit board, and the image sensor is the image sensor according to any one of claims 1 to 9; And, A lens, the lens is disposed on a side of the image sensor away from the circuit board.

11. An electronic device, characterized in that, Comprising the camera module according to claim 10.

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