TOF image sensor pixel structure and ranging system

Abstract

The present invention belongs to the technical field of image sensors, and relates to a TOF image sensor pixel structure and a ranging system, wherein the TOF image sensor pixel structure includes a first reading control module, a second reading control module and at least two small light sensors of preset sizes. The first reading control module includes at least two first transmission transistors, and the first reading control module is connected to at least two small light sensors of preset sizes in a one-to-one correspondence through at least two first transmission transistors. The second reading control module includes at least two second transmission transistors, and the second reading control module is connected to at least two small light sensors of preset sizes in a one-to-one correspondence through at least two second transmission transistors. The first transmission transistor and the second transmission transistor connected to the same small light sensor are symmetrically arranged. Therefore, the present invention can improve the transmission efficiency of photogenerated charges, and thus can achieve the purpose of improving ranging capability and ranging accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of image sensors, and in particular to a TOF image sensor pixel structure and a distance measurement system. Background Art

[0002] Image sensors are an important part of digital cameras. According to different components, image sensors can be divided into two categories: CCD (Charge Coupled Device) image sensors and CMOS (Complementary Metal Oxide Semiconductor) image sensors. Due to the advantages of CMOS image sensors such as low power consumption, low cost, and easy standardized production, they have been widely used in various fields.

[0003] With the rapid development of three-dimensional imaging information technology, especially the application of building measurement, indoor positioning and navigation, stereoscopic imaging and assisted living environment, Time-of-Flight (TOF) imaging has been urgently needed, and the pixel structure of CMOS image sensors used in time-of-flight imaging systems has also developed rapidly. TOF image sensors can be divided into dTOF image sensors and iTOF image sensors. Among them, dTOF image sensors directly measure the time of flight, that is, measure the time interval between the emitted light pulse and the received light pulse. Among them, iTOF image sensors indirectly measure the time of flight, usually using a method of measuring phase shift, that is, measuring the phase difference between the emitted sine wave / square wave and the received sine wave / square wave. For all types of TOF image sensors, ranging accuracy is an important parameter. The higher the ranging accuracy, the more accurate the three-dimensional image detection of the target.

[0004] In traditional TOF image sensor pixels, if the size of the photodiode is too large (for example, the length is too long), it will have a negative impact on the charge transfer time or transfer efficiency, which will also have a negative impact on the ranging capability and ranging accuracy.

[0005] In view of the above problems, those skilled in the art have been seeking solutions.

[0006] The preceding description is intended to provide general background information and does not necessarily constitute prior art. Summary of the invention

[0007] The technical problem to be solved by the present invention is that, in view of the defects of the above-mentioned prior art, a TOF image sensor pixel structure and a ranging system are provided to shorten the transmission time of the charge generated by the photodiode and improve the transmission efficiency of the charge generated by the photodiode, thereby achieving the purpose of improving the ranging capability and ranging accuracy.

[0008] The present invention is achieved in that:

[0009] The present invention provides a TOF image sensor pixel structure, including a first reading control module, a second reading control module and at least two small light sensors of preset sizes. The first reading control module includes at least two first transmission transistors, and the first reading control module is connected to at least two small light sensors of preset sizes in a one-to-one correspondence through at least two first transmission transistors. The second reading control module includes at least two second transmission transistors, and the second reading control module is connected to at least two small light sensors of preset sizes in a one-to-one correspondence through at least two second transmission transistors. The first transmission transistor and the second transmission transistor connected to the same small light sensor are symmetrically arranged.

[0010] Optionally, the small light sensor comprises one of a photodiode, a photogate or a photoconductor.

[0011] Optionally, the first read control module also includes a first reset transistor, a first dual conversion gain control unit, a first storage capacitor, a first node and a first output unit. The first end of the first reset transistor is connected to a voltage source, and the second end of the first reset transistor is coupled to the first node through the first dual conversion gain control unit. The first ends of at least two first transmission transistors are respectively connected to the negative electrodes of at least two small light sensors of preset sizes in a one-to-one correspondence, and the second ends of at least two first transmission transistors are connected to the first node. The first storage capacitor and the first output unit are both connected to the first node. The second read control module also includes a second reset transistor, a second dual conversion gain control unit, a second storage capacitor, a second node and a second output unit. The first end of the second reset transistor is connected to a voltage source, and the second end of the second reset transistor is coupled to the second node through the second dual conversion gain control unit. The first ends of at least two second transmission transistors are respectively connected to the negative electrodes of at least two small light sensors of preset sizes in a one-to-one correspondence, and the second ends of at least two second transmission transistors are connected to the second node. The second storage capacitor and the second output unit are both connected to the second node.

[0012] Optionally, the first output unit includes a first source follower transistor and a first row selection transistor, and the second output unit includes a second source follower transistor and a second row selection transistor. The first control terminal of the first source follower transistor is connected to the first node, the first terminal of the first source follower transistor is connected to the voltage source, and the second terminal of the first source follower transistor is connected to the first data output line through the first row selection transistor. The second control terminal of the second source follower transistor is connected to the second node, the first terminal of the second source follower transistor is connected to the voltage source, and the second terminal of the second source follower transistor is connected to the second data output line through the second row selection transistor.

[0013] Optionally, the first node is a first floating diffusion node, and the second node is a second floating diffusion node.

[0014] Optionally, a charge balancing unit is further included. The charge balancing unit is connected to the first floating diffusion node of the first read control module and the second floating diffusion node of the second read control module, and is used to balance the charges of the first floating diffusion node and the second floating diffusion node after reset.

[0015] Optionally, the first dual conversion gain control unit includes a first dual conversion gain control transistor and a first dual conversion gain capacitor. The second dual conversion gain control unit includes a second dual conversion gain control transistor and a second dual conversion gain capacitor.

[0016] Optionally, the first dual conversion gain capacitor and the second dual conversion gain capacitor are both parasitic capacitors.

[0017] Optionally, the first storage capacitor is a first dual conversion gain capacitor, and the second storage capacitor is a second dual conversion gain capacitor.

[0018] Optionally, four small light sensors are included, and the number of first transmission transistors in the first read control module and the number of second transmission transistors in the second read control module correspond to the number of the small light sensors.

[0019] Optionally, the phase difference between the first transmission transistor in the first reading control module and the second transmission transistor in the second reading control module in which they are alternately turned on during the exposure process of the light sensor is π.

[0020] Optionally, at least two anti-overflow transistors are further included, and each anti-overflow transistor corresponds to a small light sensor. The first end of each anti-overflow transistor is coupled to a voltage source, and the second end of each anti-overflow transistor is connected to the corresponding small light sensor to remove the charge generated by the background light in the corresponding small light sensor when the modulated light is not turned on.

[0021] Optionally, the preset size includes at least one of the following: 0.5x0.5um, 2.5x2.5um, 3x3um, 4X4 um.

[0022] Optionally, the shape of the small light sensor includes at least one of the following: a rectangle, a circle, or an axisymmetric shape.

[0023] Optionally, the number of small light sensors ranges from 2 to 30.

[0024] The present invention also provides a distance measurement system, comprising: an image sensor, the image sensor comprising a plurality of pixel arrays arranged in rows and columns, each pixel comprising the TOF image sensor pixel structure described above; a control signal processing unit, used to control the system operation process and process the image data acquired by the pixel array; a modulated light source, used to generate a modulated light signal after receiving a modulation signal, and feed the received modulation signal back to the pixel array.

[0025] The TOF image sensor pixel structure and ranging system provided by the present invention, wherein the TOF image sensor pixel structure includes a first reading control module, a second reading control module and at least two small light sensors of preset sizes. The first reading control module includes at least two first transmission transistors, and the first reading control module is connected to at least two small light sensors of preset sizes in a one-to-one correspondence through at least two first transmission transistors. The second reading control module includes at least two second transmission transistors, and the second reading control module is connected to at least two small light sensors of preset sizes in a one-to-one correspondence through at least two second transmission transistors. Among them, the first transmission transistor and the second transmission transistor connected to the same small light sensor are symmetrically arranged. Therefore, the present invention can save the transmission time of the charge generated by all small light sensors and improve the transmission efficiency of the charge generated by all small light sensors by using multiple small light sensors of small sizes, and the electric field generated by the symmetrically arranged first transmission transistor and the second transmission transistor can ensure the transmission rate of the charge generated by each small light sensor without the need for an additional additional driving charge transmission electric field, so the present invention can improve the transmission efficiency of the photogenerated charge, and then can achieve the purpose of improving the ranging capability and ranging accuracy.

[0026] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a first circuit schematic diagram of a TOF image sensor pixel structure provided by a first embodiment of the present invention;

[0028] Figure 2 is a second circuit schematic diagram of the TOF image sensor pixel structure provided by the first embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of the layout of the pixel structure of a TOF image sensor provided by the first embodiment of the present invention;

[0030] Figure 4 is a third circuit schematic diagram of the TOF image sensor pixel structure provided by the first embodiment of the present invention;

[0031] Figure 5 It is a schematic diagram of the structure of a distance measurement system provided by the second embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] Although the present invention uses the terms first, second, third, etc. to describe different read control modules, transfer transistors, control terminals, etc., these read control modules, transfer transistors, control terminals, etc. are not limited by these terms. These terms are only used to distinguish one read control module, transfer transistor, control terminal, etc. from another read control module, transfer transistor, control terminal, etc. Unless otherwise defined, all terms (including technical terms and scientific terms) used in the present invention have the meanings commonly understood by ordinary technicians in the field to which the present invention belongs.

[0034] In the present invention, the small light sensor can be any photosensitive structure for converting visible light into electrons (or charges, photogenerated charges), such as any one of a small photodiode PD, a small grating or a small photoconductor. Preferably, the light sensor in the present invention can be a small photodiode PD (hereinafter described using a small photodiode PD).

[0035] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0036] First embodiment:

[0037] Figure 1 is a first circuit diagram of a TOF image sensor pixel structure provided by the first embodiment of the present invention. In order to clearly describe the TOF image sensor pixel structure provided by the first embodiment of the present invention, please refer to Figure 1 .

[0038] The pixel structure of a TOF image sensor provided by the first embodiment of the present invention includes a first reading control module M1, a second reading control module M2 and at least two small photodiodes PD of a preset size.

[0039] The first read control module M1 includes at least two first transfer transistors MIX1, and the first read control module M1 is connected to at least two small photodiodes PD of preset sizes in a one-to-one correspondence through at least two first transfer transistors MIX1. The second read control module M2 includes at least two second transfer transistors MIX2, and the second read control module M2 is connected to at least two small photodiodes PD of preset sizes in a one-to-one correspondence through at least two second transfer transistors MIX2. The first transfer transistor MIX1 and the second transfer transistor MIX2 connected to the same small photodiode PD are symmetrically arranged.

[0040] In one embodiment, the first read control module M1 may further include a first reset transistor RST1, a first dual conversion gain control unit, a first storage capacitor C1, a first node Q1 and a first output unit. The first end of the first reset transistor RST1 is connected to the voltage source VDD, and the second end of the first reset transistor RST1 is coupled to the first node Q1 through the first dual conversion gain control unit. The first ends of at least two first transfer transistors MIX1 are respectively connected to the cathodes of at least two small photodiodes PD of a preset size in a one-to-one correspondence, and the second ends of at least two first transfer transistors MIX1 are both connected to the first node Q1. The first storage capacitor C1 and the first output unit are both connected to the first node Q1.

[0041] In one embodiment, the first node Q1 may be a virtual node provided for the convenience of description, or may be an actually provided floating diffusion node. When the first node Q1 is a floating diffusion node, it may be referred to as a first floating diffusion node.

[0042] In one implementation, the first reset transistor RST1 in the first read control module M1 may be used to reset a voltage (eg, reset a voltage of the first floating diffusion node or reset a voltage of the first storage capacitor C1 ) according to a reset signal.

[0043] In one implementation, the first dual conversion gain control unit in the first read control module M1 may be used to implement gain control and charge storage.

[0044] In one embodiment, the first dual conversion gain control unit in the first read control module M1 may include a first dual conversion gain control transistor DCG1 and a first dual conversion gain capacitor Cdcg1, the first dual conversion gain control transistor DCG1 is connected between the second end of the first reset transistor RST1 and the corresponding first node Q1, the first end of the first dual conversion gain capacitor Cdcg1 is coupled between the first dual conversion gain control transistor DCG1 and the first reset transistor RST1, and the second end of the first dual conversion gain capacitor Cdcg1 is connected to the voltage source VDD.

[0045] In one implementation, the first storage capacitor C1 in the first read control module M1 may serve as the first dual conversion gain capacitor Cdcg1 .

[0046] In other implementations, the first dual conversion gain control unit in the first read control module M1 may be only a first dual conversion gain control transistor DCG1 .

[0047] In other implementations, the first dual conversion gain capacitor Cdcg1 may be a parasitic capacitance between a connection point between the first reset transistor RST1 and the first dual conversion gain control transistor DCG1 and ground.

[0048] In one embodiment, the first transfer transistor MIX1 in the first read control module M1 is used to transfer the charges accumulated by the small photodiode PD.

[0049] In one embodiment, the first output unit in the first read control module M1 is used to amplify and output the voltage signal of the first node Q1 or the electrical signal of the first storage capacitor C1.

[0050] In one embodiment, the first output unit in the first read control module M1 may include a first source follower transistor SF1 and a first row select transistor RS1. The first control terminal of the first source follower transistor SF1 is connected to the first node Q1, the first terminal of the first source follower transistor SF1 is connected to the voltage source VDD, and the second terminal of the first source follower transistor SF1 is connected to the first data output line BL1 through the first row select transistor RS1.

[0051] In one embodiment, the second read control module M2 further includes a second reset transistor RST2, a second dual conversion gain control unit, a second storage capacitor C2, a second node Q2 and a second output unit. The first end of the second reset transistor RST2 is connected to the voltage source VDD, and the second end of the second reset transistor RST2 is coupled to the second node Q2 through the second dual conversion gain control unit. The first ends of at least two second transmission transistors MIX2 are respectively connected to the cathodes of at least two small photodiodes PD of a preset size in a one-to-one correspondence, and the second ends of at least two second transmission transistors MIX2 are both connected to the second node Q2. The second storage capacitor C2 and the second output unit are both connected to the second node Q2.

[0052] In one embodiment, the second node Q2 may be a virtual node provided for the convenience of description, or may be an actually provided floating diffusion node. When the second node Q2 is a floating diffusion node, it may be referred to as a second floating diffusion node.

[0053] In one implementation, the second reset transistor RST2 in the second read control module M2 may be used to reset the voltage (eg, reset the voltage of the second floating diffusion node FD2 or reset the voltage of the second storage capacitor C2 ) according to the reset control signal.

[0054] In one implementation, the second dual conversion gain control unit in the second read control module M2 may be used to implement gain control and charge storage.

[0055] In one embodiment, the second dual conversion gain control unit in the second read control module M2 may include a second dual conversion gain control transistor DCG2 and a second dual conversion gain capacitor Cdcg2, the second dual conversion gain control transistor DCG2 is coupled between the second end of the second reset transistor RST2 and the corresponding second node Q2, the second end of the second dual conversion gain capacitor Cdcg2 is coupled between the second dual conversion gain control transistor DCG2 and the second reset transistor RST2, and the second end of the second dual conversion gain capacitor Cdcg2 is connected to the voltage source VDD.

[0056] In one implementation, the second storage capacitor in the second read control module may serve as the second dual conversion gain capacitor Cdcg2 .

[0057] In other embodiments, the second dual conversion gain capacitor Cdcg2 is a parasitic capacitance between a connection point between the second reset transistor RST2 and the second dual conversion gain control transistor DCG2 and ground.

[0058] In one embodiment, the second transfer transistor MIX2 in the second read control module M2 is used to transfer the charges accumulated by the small photodiode PD.

[0059] In one embodiment, the second transfer transistor MIX2 of the second read control unit M2 and the first transfer transistor MIX1 of the first read control unit M1 are alternately turned on during the exposure process of the small photodiode PD to alternately transfer the charge accumulated in the small photodiode PD to the second floating diffusion node FD2 (or the first storage capacitor C1) or the first floating diffusion node FD1 (or the second storage capacitor C2). Specifically, in this embodiment, by setting the first read control module M1 and the second read control module M2 to be coupled to the small photodiode PD respectively, and controlling the first transfer transistor MIX1 and the second transfer transistor MIX2 to be alternately turned on during the exposure process of the small photodiode PD to alternately transfer the charge accumulated in the small photodiode PD to the corresponding floating diffusion node (or storage capacitor), the effective light signal accumulated in the floating diffusion node (or storage capacitor) corresponding to the first read control module M1 and the second read control module M2 can be calculated, and the flight time of the light pulse can be determined, so that the pixel structure can be suitable for image sensors with TOF technology. And because the first read control module M1 and the second read control module M2 use transfer transistors to couple the small photodiode PD with the corresponding floating diffusion node (or storage capacitor), the charge accumulated in the small photodiode PD is transferred to the floating diffusion node (storage capacitor) through the transfer transistor, so that the pixel structure can support the rolling exposure mode.

[0060] In one embodiment, the second transfer transistor MIX2 in the second read control module M2 and the first transfer transistor MIX1 in the first read control module M1 are alternately turned on in a phase difference of π during the exposure process of the small photodiode PD.

[0061] In one embodiment, the second output unit in the second read control module M2 is used to amplify and output the voltage signal of the second floating diffusion node FD2 or the second storage capacitor C2.

[0062] In one embodiment, the second output unit in the second read control module M2 includes a second source follower transistor SF2 and a second row select transistor RS2. The second control terminal of the second source follower transistor SF2 is connected to the second node, the first terminal of the second source follower transistor SF2 is connected to the voltage source VDD, and the second terminal of the second source follower transistor SF2 is connected to the second data output line BL2 through the second row select transistor RS2.

[0063] In one implementation, the second reading control module M2 and the first reading control module M1 may be symmetrically arranged in the substrate of the TOF image sensor pixel structure provided in this embodiment.

[0064] Figure 2 4 is a second circuit diagram of the TOF image sensor pixel structure provided by the first embodiment of the present invention.

[0065] See also Figure 2 In one implementation, the pixel structure of the TOF image sensor provided in the first embodiment of the present invention may include, for example, four small photodiodes PD, and the number of first transfer transistors MIX1 in the first reading control module M1 and the number of second transfer transistors MIX2 in the second reading control module M2 correspond to the number of small photodiodes PD. Specifically, the four small photodiodes PD are connected in parallel through the four first transfer transistors MIX1 in the first reading control module M1 and the four second transfer transistors MIX2 in the second reading control module M2.

[0066] In one embodiment, at least two small photodiodes PD (for example, four small photodiodes PD) in this embodiment can be understood as splitting a traditional large-sized photodiode into a plurality of small photodiodes PD for parallel connection. The TOF image sensor pixel structure provided in this embodiment can save the transmission time of the charges generated by all small photodiodes PD and improve the transmission efficiency of the charges generated by all small photodiodes PD by using a plurality of small-sized small photodiodes PD, and the electric field generated by the symmetrically arranged first transfer transistor MIX1 and the second transfer transistor MIX2 can ensure the transmission rate of the charges generated by each small photodiode PD without the need for an additional additional electric field for driving the charge transmission. Therefore, the TOF image sensor pixel structure provided in this embodiment can improve the transmission efficiency of the photogenerated charges, and thus can achieve the purpose of improving the ranging capability and ranging accuracy.

[0067] Figure 3 Schematic diagram of the layout of the pixel structure of the TOF image sensor provided by the first embodiment of the present invention.

[0068] See also Figure 3 In one embodiment, the small photodiode PD, the first read control module M1 and the read control module M2 in the TOF image sensor pixel structure provided in the first embodiment of the present invention can be symmetrically arranged in the substrate. For example, four small photodiodes PD are symmetrically arranged in the substrate, and the first transfer transistor MIX1, the first reset transistor RST1, the first dual conversion gain control transistor DCG1, the first source follower transistor SF1 and the first row selection transistor RS1 in the first read control module M1, and the second transfer transistor MIX2, the second reset transistor RST2, the second dual conversion gain control transistor DCG2, the second source follower transistor SF2 and the second row selection transistor RS2 in the second read control module M2 are symmetrically arranged in the substrate.

[0069] Figure 44 is a third circuit diagram of the TOF image sensor pixel structure provided by the first embodiment of the present invention.

[0070] See also Figure 4 In one implementation, the TOF image sensor pixel structure provided by the first embodiment of the present invention may further include a charge balancing unit EQ. The charge balancing unit EQ may be connected to the first floating diffusion node FD1 of the first read control module M1 and the second floating diffusion node FD2 of the second read control module M2, and is used to balance the charges of the first floating diffusion node FD1 and the second floating diffusion node FD2 after reset. Therefore, this embodiment can ensure that the voltages of several floating diffusion nodes in the TOF image sensor pixel are equal after reset, thereby improving the ranging accuracy of the image sensor.

[0071] In other embodiments, the charge balancing unit EQ may be connected to the first node Q1 of the first read control module M1 and the second node Q2 of the second read control module M2, for balancing the charges of the first storage capacitor C1 and the second storage capacitor C2 after resetting. Therefore, this embodiment can ensure that the voltages of several storage capacitors in the TOF image sensor pixel are equal after resetting, thereby improving the ranging accuracy of the image sensor.

[0072] In addition, in one embodiment, the TOF image sensor pixel structure provided by the first embodiment of the present invention may also include at least two anti-overflow transistors (all shown in the figure), and each anti-overflow transistor corresponds to a small photodiode PD. The first end of each anti-overflow transistor is coupled to the voltage source VDD, and the second end of each anti-overflow transistor is connected to the corresponding small photodiode PD to remove the charge generated by the background light in the corresponding small photodiode PD when the modulated light is not turned on. Specifically, when the modulated light is not turned on, the anti-overflow transistor is turned on to eliminate the unwanted background light signal, avoid the background light charge from being transferred to the floating diffusion node, thereby suppressing the background light, thereby improving the ranging accuracy.

[0073] In one embodiment, the preset size of the small photodiode PD may include at least one of the following: 0.5x0.5um, 2.5x2.5um, 3x3um, 4X4um.

[0074] In one embodiment, the shape of the small photodiode PD may include at least one of the following: a rectangle, a circle, or an axisymmetric figure (eg, an axisymmetric polygon).

[0075] In one embodiment, the number of small photodiodes PD may range from 2 to 30.

[0076] The pixel structure of a TOF image sensor provided by the first embodiment of the present invention includes a first reading control module M1, a second reading control module M2 and at least two small photodiodes PD of a preset size. The first reading control module M1 includes at least two first transfer transistors MIX1, and the first reading control module M1 is connected to at least two small photodiodes PD of a preset size in a one-to-one correspondence through at least two first transfer transistors MIX1. The second reading control module M2 includes at least two second transfer transistors MIX2, and the second reading control module M2 is connected to at least two small photodiodes PD of a preset size in a one-to-one correspondence through at least two second transfer transistors MIX2. The first transfer transistor MIX1 and the second transfer transistor MIX2 connected to the same small photodiode PD are symmetrically arranged. Therefore, the TOF image sensor pixel structure provided in the first embodiment of the present invention can save the transmission time of the charges generated by all small photodiodes PD and improve the transmission efficiency of the charges generated by all small photodiodes PD by using multiple small-sized small photodiodes PD, and the electric field generated by the symmetrically arranged first transfer transistor MIX1 and the second transfer transistor MIX2 can ensure the transmission rate of the charges generated by each small photodiode PD without the need for an additional electric field for driving the charge transmission. Therefore, the TOF image sensor pixel structure provided in the first embodiment of the present invention can improve the transmission efficiency of the photogenerated charges, and thus can achieve the purpose of improving the ranging capability and ranging accuracy.

[0077] Second embodiment:

[0078] Figure 5 is a schematic diagram of the structure of the distance measurement system provided by the second embodiment of the present invention. In order to clearly describe the distance measurement system provided by the second embodiment of the present invention, please refer to Figure 5 .

[0079] The distance measurement system provided by the second embodiment of the present invention includes: an image sensor 10 , a control signal processing unit 11 and a modulatable light source 12 .

[0080] The image sensor 10 includes a plurality of pixel arrays arranged in rows and columns, and each pixel includes the TOF image sensor pixel structure described in the first embodiment.

[0081] The control signal processing unit 11 is used to control the system working process and process the image data acquired by the pixel array.

[0082] The modulated light source 12 is used to generate a modulated light signal after receiving a modulation signal, and feed back the received modulation signal to the pixel array.

[0083] The ranging system provided by the second embodiment of the present invention has a TOF image sensor pixel structure of an image sensor including at least a first reading control module M1, a second reading control module M2 and at least two small photodiodes PD of a preset size. The first reading control module M1 includes at least two first transfer transistors MIX1, and the first reading control module M1 is connected to at least two small photodiodes PD of a preset size in a one-to-one correspondence through at least two first transfer transistors MIX1. The second reading control module M2 includes at least two second transfer transistors MIX2, and the second reading control module M2 is connected to at least two small photodiodes PD of a preset size in a one-to-one correspondence through at least two second transfer transistors MIX2. The first transfer transistor MIX1 and the second transfer transistor MIX2 connected to the same small photodiode PD are symmetrically arranged. Therefore, the ranging system provided by the second embodiment of the present invention can improve the transmission efficiency of photogenerated charges, and thus can achieve the purpose of improving ranging capability and ranging accuracy.

[0084] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] It should be noted that, in this article, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, component or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article, component or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other identical elements in the process, method, article, component or device including the element. In addition, components, features, and elements with the same name in different embodiments of the present application may have the same meaning or different meanings, and their specific meanings need to be determined by their explanation in the specific embodiment or further combined with the context of the specific embodiment.

[0086] It should be understood that, although the terms first, second, third, etc. may be used to describe various information in this article, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. Depending on the context, the word "if" as used herein can be interpreted as "at the time of..." or "when..." or "in response to determination". Moreover, as used in this article, the singular forms "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. It should be further understood that the terms "comprising", "including" indicate that there are the described features, steps, operations, elements, components, projects, kinds, and / or groups, but do not exclude the existence, occurrence or addition of one or more other features, steps, operations, elements, components, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some manner.

[0087] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A TOF image sensor pixel structure, characterized in that: It includes a first reading control module, a second reading control module and at least two small optical sensors of preset sizes, wherein the shape of the small optical sensors includes an axisymmetric figure, and the axisymmetric figure includes a rectangle or a circle; The first read control module includes at least two first transmission transistors, a first reset transistor, a first dual conversion gain control unit, a first storage capacitor, a first node and a first output unit; Wherein, the first end of the first reset transistor is connected to a voltage source, and the second end of the first reset transistor is coupled to the first node through the first dual conversion gain control unit; The first ends of the at least two first transmission transistors are respectively connected to the negative electrodes of the at least two small light sensors of preset sizes in a one-to-one correspondence, and the second ends of the at least two first transmission transistors are both connected to the first node; The first storage capacitor and the first output unit are both connected to the first node; The second read control module includes at least two second transmission transistors, a second reset transistor, a second dual conversion gain control unit, a second storage capacitor, a second node and a second output unit; Wherein, a first terminal of the second reset transistor is connected to the voltage source, and a second terminal of the second reset transistor is coupled to the second node through the second dual conversion gain control unit; The first ends of the at least two second transmission transistors are respectively connected to the negative electrodes of the at least two small light sensors of preset sizes in a one-to-one correspondence, and the second ends of the at least two second transmission transistors are both connected to the second node; The second storage capacitor and the second output unit are both connected to the second node; The first transmission transistor and the second transmission transistor connected to the same small light sensor are symmetrically arranged.

2. The TOF image sensor pixel structure according to claim 1, wherein: The small light sensor includes one of a photodiode, a photogate, or a photoconductor.

3. The TOF image sensor pixel structure according to claim 1, wherein: The first output unit includes a first source follower transistor and a first row selection transistor, and the second output unit includes a second source follower transistor and a second row selection transistor; A first control terminal of the first source follower transistor is connected to the first node, a first terminal of the first source follower transistor is connected to the voltage source, and a second terminal of the first source follower transistor is connected to a first data output line through the first row selection transistor; The second control terminal of the second source follower transistor is connected to the second node, the first terminal of the second source follower transistor is connected to the voltage source, and the second terminal of the second source follower transistor is connected to the second data output line through the second row selection transistor.

4. The TOF image sensor pixel structure according to claim 1 or 3, characterized in that: The first node is a first floating diffusion node, and the second node is a second floating diffusion node.

5. The TOF image sensor pixel structure according to claim 4, characterized in that: Also included is a charge balancing unit; The charge balancing unit is connected to the first floating diffusion node of the first read control module and the second floating diffusion node of the second read control module, and is used to balance the charges of the first floating diffusion node and the second floating diffusion node after reset.

6. The TOF image sensor pixel structure according to claim 1, wherein: The first dual conversion gain control unit includes a first dual conversion gain control transistor and a first dual conversion gain capacitor; The second dual conversion gain control unit includes a second dual conversion gain control transistor and a second dual conversion gain capacitor.

7. The TOF image sensor pixel structure according to claim 6, wherein: The first dual conversion gain capacitor and the second dual conversion gain capacitor are both parasitic capacitors.

8. The TOF image sensor pixel structure according to claim 1, wherein: The first storage capacitor is a first dual conversion gain capacitor, and the second storage capacitor is a second dual conversion gain capacitor.

9. The TOF image sensor pixel structure according to claim 1, wherein: Four small light sensors are included, and the number of first transmission transistors in the first read control module and the number of second transmission transistors in the second read control module correspond to the number of the small light sensors.

10. The TOF image sensor pixel structure according to claim 1, wherein: The first transmission transistor in the first reading control module and the second transmission transistor in the second reading control module are alternately turned on in the exposure process of the light sensor with a phase difference of π.

11. The TOF image sensor pixel structure according to claim 1, wherein: It also includes at least two anti-overflow transistors, and each of the anti-overflow transistors corresponds to one of the small light sensors; A first terminal of each anti-overflow transistor is coupled to a voltage source, and a second terminal of each anti-overflow transistor is connected to the corresponding small light sensor to remove charges generated by background light from the corresponding small light sensor when the modulated light is not turned on.

12. The TOF image sensor pixel structure according to claim 1, wherein: The preset size includes at least one of the following: 0.5x0.5um, 2.5x2.5um, 3x3um, 4X4 um.

13. The TOF image sensor pixel structure according to claim 1, wherein: The number of the small light sensors ranges from 2 to 30.

14. A distance measurement system, characterized in that: include: An image sensor, the image sensor comprising a plurality of pixel arrays arranged in rows and columns, each pixel comprising a TOF image sensor pixel structure as claimed in any one of claims 1 to 13; A control signal processing unit, used to control the system working process and process the image data acquired by the pixel array; The modulated light source is used to generate a modulated light signal after receiving a modulation signal, and feed back the received modulation signal to the pixel array.

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