Control circuit of image sensor and image sensor
By designing the control circuit of the image sensor, including a roller shutter exposure and global exposure finite state machine, and a timing signal generation module, the problem of difficulty in compatibility with roller shutter exposure and global exposure modes in the prior art is solved, and two exposure modes are supported in one system at the same time, improving the flexibility and applicability of the system.
Patent Information
- Application Number
- CN202311785552.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-22
- Publication Date
- 2025-06-24
AI Technical Summary
The prior art is difficult to compatible with two exposure modes in a system: roller shutter exposure and global exposure, resulting in technical challenges when compatible with two working modes.
A control circuit for an image sensor is designed, including digital control circuit, analog circuit and output circuit. The digital control circuit includes a roller shutter exposure finite state machine and a global exposure finite state machine to generate a state indication signal adapted to different exposure modes. The timing signal generation module generates corresponding timing signals based on these state indication signals, and the analog circuit selects pixel areas according to the timing signal for exposure and converts the analog signal into a digital signal.
It realizes the support of roller shutter exposure and global exposure in a system, which meets different needs for shooting dynamic objects and static objects, and improves the flexibility and applicability of the system.
Smart Images
Figure CN120201324A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of image sensors, and in particular to a control circuit of an image sensor; and also to an image sensor. Background Art
[0002] CMOS image sensors are divided into two exposure modes, one is the rolling shutter exposure mode, which exposes row by row or column by column, suitable for high-definition shooting of static objects or slow-moving objects, with a high frame rate. The other is the global exposure mode, which exposes the entire image area at the same time, which can be used to take pictures or videos of dynamic objects, with a lower frame rate at the same exposure time. Due to the differences in the process from exposure to readout, these two exposure modes each correspond to a set of circuit architecture designs. Rolling shutter exposure requires selecting row / column pixel arrays with different addresses to start exposure, and ends exposure when the corresponding address is selected to read out data. Global exposure selects the entire image for exposure, and a period of pre-frame time is required before data can be read out before reading can begin.
[0003] In view of the differences in the exposure processes of the two exposure modes, when the two exposure working modes need to be compatible, providing a control circuit that supports controlling the two exposure modes has become a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention
[0004] The purpose of the present application is to provide a control circuit of an image sensor, which supports controlling two exposure modes, and can realize rolling exposure and global exposure in one system. Another purpose of the present application is to provide an image sensor, which also has the above technical effects.
[0005] In order to solve the above technical problems, the present application provides a control circuit of an image sensor, comprising:
[0006] A digital control circuit, an analog circuit and an output circuit; the digital control circuit includes a rolling exposure finite state machine, a global exposure finite state machine and a timing signal generation module; the output circuit includes an interface circuit;
[0007] The rolling shutter exposure finite state machine is used to generate a first state indication signal adapted to the rolling shutter exposure mode;
[0008] The global exposure finite state machine is used to generate a second state indication signal adapted to the global exposure mode;
[0009] The timing signal generating module is used to generate a first timing signal according to the first state indication signal, and to generate a second timing signal according to the second state indication signal;
[0010] The analog circuit is used to select a pixel region for exposure according to the first timing signal, select a pixel region for exposure according to the second timing signal, and convert the read analog signal into a digital signal;
[0011] The output circuit is used for data output.
[0012] Optionally, the analog circuit includes:
[0013] A rolling shutter exposure address decoder, which is used to select a pixel region for exposure according to the first timing signal and register configuration;
[0014] A global exposure address decoder, which is used to select a pixel region for exposure according to the second timing signal and register configuration;
[0015] An analog-to-digital conversion module, which is used to convert the read analog signal into a digital signal.
[0016] Optionally, in the rolling shutter mode, the same exposure unit sequentially experiences an exposure state, a readout state, and an output state; wherein, the exposure states of different exposure units in the same frame do not overlap, the readout states of different exposure units in the same frame do not overlap, and the output states of different exposure units in the same frame do not overlap; the exposure unit is a row or a column.
[0017] Optionally, in the global exposure mode, each frame sequentially experiences an exposure state, a pre-frame time, a readout state, and an output state; wherein, the exposure state of the next frame does not overlap with the pre-frame time of the previous frame, the readout states of different exposure units in the same frame do not overlap, and the output states of different exposure units in the same frame do not overlap; the exposure unit is a row or a column.
[0018] Optionally, the digital control circuit further includes:
[0019] A register configuration module, which is used to configure registers.
[0020] Optionally, the digital control circuit further includes:
[0021] A dark level automatic correction module, which is used to perform dark level correction.
[0022] Optionally, the analog circuit further includes:
[0023] A phase-locked loop, which is used to generate a working clock according to a reference clock.
[0024] Optionally, the analog circuit further includes:
[0025] A power-on reset module, which is used to perform power-on reset.
[0026] Optionally, the analog circuit further includes:
[0027] A temperature sensor for monitoring temperature.
[0028] To solve the above technical problems, the present application also provides an image sensor, including the control circuit of the image sensor as described above.
[0029] The control circuit of the image sensor provided by the present application includes: a digital control circuit, an analog circuit, and an output circuit; the digital control circuit includes a rolling shutter exposure finite state machine, a global exposure finite state machine, and a timing signal generation module; the output circuit includes an interface circuit; the rolling shutter exposure finite state machine is used to generate a first state indication signal adapted to the rolling shutter exposure mode; the global exposure finite state machine is used to generate a second state indication signal adapted to the global exposure mode; the timing signal generation module is used to generate a first timing signal according to the first state indication signal and a second timing signal according to the second state indication signal; the analog circuit is used to select a pixel region for exposure according to the first timing signal, select a pixel region for exposure according to the second timing signal, and convert the read analog signal into a digital signal; the output circuit is used for data output.
[0030] It can be seen that for the control circuit of the image sensor provided by the present application, the rolling shutter exposure finite state machine and the global exposure finite state machine in the digital control circuit can respectively generate state indication signals adapted to the rolling shutter exposure mode and the global exposure mode, and the timing signal generation module in the digital control circuit generates corresponding timing signals according to the state indication signals. The analog circuit selects a pixel region for exposure according to the timing signals and converts the read analog signal into a digital signal. The output circuit is used for data output. In this way, it is possible to support rolling shutter exposure and global exposure in a single system.
[0031] The image sensor provided by the present application also has the above technical effects. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the prior art and the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0033] Figure 1 It is a schematic diagram of a control circuit of an image sensor provided by an embodiment of the present application;
[0034] Figure 2 It is a schematic diagram of another control circuit of an image sensor provided by an embodiment of the present application;
[0035] Figure 3 A rolling shutter exposure timing diagram provided by an embodiment of the present application;
[0036] Figure 4 A global exposure timing diagram provided by an embodiment of the present application. Specific embodiments
[0037] The core of the present application is to provide a control circuit for an image sensor, which supports controlling two exposure modes and can realize supporting rolling shutter exposure and global exposure in a set of systems. Another core of the present application is to provide an image sensor, which also has the above technical effects.
[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.
[0039] Please refer to Figure 1 , Figure 1 A schematic diagram of a control circuit for an image sensor provided by an embodiment of the present application. Referring to Figure 1 shown, the control circuit includes:
[0040] A digital control circuit 10, an analog circuit 20, and an output circuit 30; the digital control circuit 10 includes a rolling shutter finite state machine 101, a global exposure finite state machine 102, and a timing signal generation module 103; the output circuit 30 includes an interface circuit 301;
[0041] The rolling shutter finite state machine 101 is used to generate a first state indication signal adapted to the rolling shutter exposure mode;
[0042] The global exposure finite state machine 102 is used to generate a second state indication signal adapted to the global exposure mode;
[0043] The timing signal generation module 103 is used to generate a first timing signal according to the first state indication signal and generate a second timing signal according to the second state indication signal;
[0044] The analog circuit 20 is used to select a pixel area for rolling shutter exposure and reading according to the first timing signal, select a pixel area for global exposure and reading according to the second timing signal, and convert the read analog signal into a digital signal;
[0045] The output circuit 30 is used for data output.
[0046] In this embodiment, the control circuit includes a digital control circuit 10, an analog circuit 20, and an output circuit 30. The digital control circuit 10 includes two finite state machines, namely a rolling shutter exposure finite state machine 101 and a global exposure finite state machine 102, and a timing signal generation module 103. The output circuit 30 includes an interface circuit 301. The status indication signal is a signal used to indicate the status of the exposure process. The digital control circuit 10 controls the switching of different exposure processes by generating status indication signals adapted to different exposure modes, and generates timing signals according to the status indication signals. The analog circuit 20 selects a pixel area for exposure according to the timing signals.
[0047] In the rolling shutter exposure mode, the exposure process includes three states: exposure (EXPT), readout (READ), and output (DATAOUT). In the global exposure mode, the exposure process includes four states: exposure (EXPT), frame overhead time (FOT), readout (READ), and output (DATAOUT). In this embodiment, the same set of control signals is used for the two exposure processes, and different exposure areas are selected for photoelectric conversion. The full English name of FOT is Frame overhead time, which is a time state between exposure and readout. During this time, the exposed signals are stored on the storage nodes in the pixels at the same time, and then the stored signals are read out during the readout stage.
[0048] The finite state machines (including the rolling shutter exposure finite state machine 101 and the global exposure finite state machine 102) use different encodings to represent the states of the exposure process. For example, 0 is used to represent exposure, 1 is used to represent frame overhead time, 2 is used to represent readout, and 3 is used to represent output. When the state jumps, the status indication signal changes accordingly. The state jump of the finite state machine can be triggered by a frame request signal. For example, when the frame request signal is at a high level, it triggers the state jump of the finite state machine and enters the EXPT state. When the frame request signal is pulled low, the finite state machine jumps from the EXPT state to the FOT state.
[0049] The important timing signals related to rolling shutter exposure include read clock / read address, exposure clock / exposure address, exposure indication signal, reset signal, etc. The important timing signals related to global exposure include read clock / read address, exposure indication signal, reset signal, etc.
[0050] The two exposure modes share the timing signal generation module 103. The timing signal generation module 103 generates timing signals according to the status indication signals and the timing register. By configuring the timing register, the change situation of a certain timing signal under a certain state can be agreed upon.
[0051] For example, for the signal CSEL_ST used to indicate the data output time, by configuring the timing register, the signal CSEL_ST changes from 0 to 1 at the first digital clock rising edge in the READ state and from 0 to 1 at the second digital clock rising edge. For example, bit
[15] of the timing register csel_st_c00[15:0] indicates whether it is from 0 to 1 or from 1 to 0, bit
[14] indicates the default value, and bits [13:0] indicate which clock rising edge the change occurs at. If csel_st_c00 = 1_0_00000000000000, it means it changes from 0 to 1 at the first digital clock rising edge; if csel_st_c00 = 0_0_00000000000001, it means it changes from 0 to 1 at the second digital clock rising edge. In actual circuit implementation, a counter can be used, which only counts when state = READ. When the counter = 0, the signal CSEL_ST rises; when the counter = 1, the signal CSEL_ST falls.
[0052] In some embodiments, the digital control circuit 10 further includes:
[0053] A register configuration module for configuring registers.
[0054] The exposure mode, exposure time, output frame size, the way to trigger exposure, frame rate, etc. are all configured by the register configuration module.
[0055] In some embodiments, the digital control circuit 10 further includes:
[0056] A dark level automatic correction module for performing dark level correction.
[0057] In the pixel array, some areas are covered by a light shield and are affected by dark current / level interference. Pixels in these areas can also have brightness information. The effective pixel part with normal light intake is also affected by dark current / level interference, so it needs to be corrected. After counting the dark pixels, through an algorithm, it can be calculated how many pixel values need to be corrected, added, or subtracted for the effective pixel part to achieve dark level automatic correction.
[0058] The analog circuit 20 selects different pixel areas for exposure according to the register configuration transmitted from the digital control circuit 10 and the timing signal. After the exposure ends, the analog circuit 20 converts the read analog quantity into pixel values, stores them in the RAM, and waits for the signal CSEL_ST to indicate the data output time before outputting.
[0059] In some embodiments, the analog circuit 20 includes:
[0060] A rolling shutter exposure address decoder 201 for selecting a pixel area for exposure according to the first timing signal and the register configuration;
[0061] A global exposure address decoder 202 is configured to select a pixel region for exposure according to the second timing signal and the register configuration;
[0062] An analog-to-digital conversion module 203 is configured to convert the read analog signal into a digital signal.
[0063] Reference Figure 2 As shown, if the exposure mode is rolling shutter exposure, the rolling shutter exposure address decoder 201 selects a rolling shutter exposure pixel region for exposure. If the exposure mode is global exposure, the global exposure address decoder 202 selects a global exposure pixel region for exposure and readout. After the exposure ends, the analog-to-digital conversion module 203 converts the read analog signal into a pixel value and stores it in the RAM, waiting for the signal CSEL_ST to indicate the moment of data output before outputting.
[0064] For example, register = 0 represents rolling shutter exposure, and register = 1 represents global exposure. Row addresses 0 to 479 are the rolling shutter exposure pixel regions, and row addresses 480 to 959 are the global exposure pixel regions. When the register = 0, it indicates that the exposure mode is rolling shutter exposure, and the rolling shutter exposure address decoder selects a rolling shutter exposure pixel region for exposure. When the register = 1, it indicates that the exposure mode is global exposure, and the global exposure address decoder selects a global exposure pixel region for exposure.
[0065] In some embodiments, the analog circuit 20 further includes:
[0066] A phase-locked loop for generating a working clock according to a reference clock.
[0067] A power-on reset module for performing power-on reset.
[0068] A temperature sensor for monitoring temperature.
[0069] The phase-locked loop generates different working clocks internally according to an externally input reference clock. The power-on reset module is used to implement the power-on reset function. The temperature sensor is used to monitor the system temperature.
[0070] The output circuit 30 processes the data. The functions of the output circuit 30 may include replacing test patterns, dark current correction bias, digital gain, digital format encoding, etc., that is, the output circuit 30 can perform processing such as dark current correction and digital gain on the input data. The output circuit 30 converts the data into parallel data conforming to the data transmission protocol. The interface circuit 301 in the output circuit 30 converts the parallel data into serial data and then outputs it. The parallel data is converted into a serial high-frequency signal by the high-frequency clock generated by the phase-locked loop and output. The serial high-frequency signal conforms to a high-speed communication protocol, such as MIPI or LVDS.
[0071] The control circuit described in the above embodiments can be applied to a pixel array in which a rolling shutter exposure pixel region and a global exposure pixel region are arranged. Different regions of the pixel array cover a color filter array, generating four pixel patterns of red, green, blue, and white. Among them, the color filters in the upper and lower half regions of the pixel array are the same. The upper half region is the global exposure pixel region, and the lower half region is the rolling shutter exposure pixel region. Due to different pixel processes, the area of each pixel unit is inconsistent. In the same shooting scenario, different regions and exposure mechanisms can be applied to achieve different image effects.
[0072] In some embodiments, in the rolling shutter exposure mode, the same exposure unit sequentially experiences an exposure state, a read state, and an output state; wherein, the exposure states of different exposure units in the same frame do not overlap, the read states of different exposure units in the same frame do not overlap, and the output states of different exposure units in the same frame do not overlap; the exposure unit is a row or a column.
[0073] Taking the exposure unit as a row as an example: Refer to Figure 3 the rolling shutter exposure timing diagram shown. Each row of data in the rolling shutter exposure experiences the following 3 states from exposure to reading: exposure (EXPT), reading (READ), and output (DATAOUT). ROW1 represents the entire exposure process of the first row, and Frame1 represents the entire exposure process of the first frame. During EXPT, the digital control circuit 10 generates an exposure clock to sample the exposure address. If the exposure address corresponds to the pixel array ROW1, then ROW1 starts to be exposed. When the digital control circuit 10 generates a read clock to sample the read address of ROW1, it enters the READ state. When the digital control circuit 10 generates the signal CSEL_ST, data reading starts. ROW2 starts to be exposed after ROW1, and its states are denoted as EXPT2, READ2, and DATA2 (the principle is the same as that of ROW1). Among them, READ2 cannot overlap with READ1 because the analog-to-digital conversion module cannot read two read addresses simultaneously and store them in the RAM. DATA2 cannot overlap with DATA1 because two rows of data cannot be output simultaneously. Similarly, two rows cannot be exposed simultaneously in the same frame. The interval between ROW2 and ROW1, that is, the row period, is determined by the output period.
[0074] In some embodiments, in the global exposure mode, each frame sequentially experiences an exposure state, a pre-frame time, a read state, and an output state; wherein, the exposure state of the next frame does not overlap with the pre-frame time of the previous frame, the read states of different exposure units in the same frame do not overlap, and the output states of different exposure units in the same frame do not overlap; the exposure unit is a row or a column.
[0075] Taking the exposure unit as a row as an example: Refer to Figure 4The global exposure timing diagram shown. For each frame of data in global exposure, from exposure to readout, it has to go through the following 4 states: exposure (EXPT), frame pre (FOT), readout (READ), and output (DATAOUT). Compared with rolling shutter exposure, it has one more FOT state. During EXPT, the digital control circuit 10 generates a low-effective exposure indication signal, indicating that the 4 color regions on the pixel array all start to be exposed. When the digital control circuit 10 raises the exposure indication signal, it enters the FOT state. When the digital control circuit 10 generates a read clock to sample the read address, it enters the READ state. When the digital control circuit 10 generates CSEL_ST, it starts to read out data. Among them, the EXPT of the next frame cannot overlap with the FOT of the previous frame, the readout states of different rows in the same frame do not overlap, and the output states of different rows in the same frame do not overlap.
[0076] In summary, for the control circuit of the image sensor provided in this application, the rolling shutter exposure finite state machine and the global exposure finite state machine in the digital control circuit can respectively generate state indication signals adapted to the rolling shutter exposure mode and the global exposure mode. The timing signal generation module in the digital control circuit generates corresponding timing signals according to the state indication signals. The analog circuit selects pixel regions for exposure according to the timing signals and converts the read analog signals into digital signals. The output circuit is used for data output. In this way, it can support both rolling shutter exposure and global exposure in one system.
[0077] This application also provides an image sensor, which includes the control circuit of the image sensor as described in the above embodiment. For the image sensor, reference can be made to the above embodiment of the control circuit, and details will not be repeated here.
[0078] For the image sensor provided in this application, the rolling shutter exposure finite state machine and the global exposure finite state machine in the digital control circuit can respectively generate state indication signals adapted to the rolling shutter exposure mode and the global exposure mode. The timing signal generation module in the digital control circuit generates corresponding timing signals according to the state indication signals. The analog circuit selects pixel regions for exposure according to the timing signals and converts the read analog signals into digital signals. The output circuit is used for data output. In this way, it can support both rolling shutter exposure and global exposure in one system.
[0079] The various embodiments in the specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.
[0080] Those skilled in the art may further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described according to their functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods for each specific application to implement the described functions, but such implementation should not be considered as exceeding the scope of this application.
[0081] The steps of the methods or algorithms described in combination with the embodiments disclosed herein can be directly implemented by hardware, software modules executed by a processor, or a combination of both. The software modules can be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.
[0082] The control circuit and image sensor of the image sensor provided in this application have been introduced in detail above. Specific examples are used herein to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the method and its core idea of this application. It should be noted that for those of ordinary skill in the art, without departing from the principle of this application, several improvements and modifications can be made to this application, and these improvements and modifications also fall within the protection scope of the claims of this application.
Claims
1. A control circuit for an image sensor, characterized in that, Comprising: A digital control circuit, an analog circuit, and an output circuit; the digital control circuit includes a rolling shutter exposure finite state machine, a global exposure finite state machine, and a timing signal generation module; The output circuit includes an interface circuit; The rolling shutter exposure finite state machine is used to generate a first state indication signal adapted to the rolling shutter exposure mode; The global exposure finite state machine is used to generate a second state indication signal adapted to the global exposure mode; The timing signal generation module is used to generate a first timing signal according to the first state indication signal and generate a second timing signal according to the second state indication signal; The analog circuit is used to select a pixel region for exposure according to the first timing signal, select a pixel region for exposure according to the second timing signal, and convert the read analog signal into a digital signal; The output circuit is used for data output.
2. The control circuit of the image sensor according to claim 1, characterized in that The analog circuit includes: A rolling shutter exposure address decoder for selecting a pixel region for exposure according to the first timing signal and register configuration; A global exposure address decoder for selecting a pixel region for exposure according to the second timing signal and register configuration; An analog-to-digital conversion module for converting the read analog signal into a digital signal.
3. The control circuit of the image sensor according to claim 1, wherein In the rolling shutter exposure mode, the same exposure unit sequentially experiences an exposure state, a readout state, and an output state; wherein, the exposure states of different exposure units in the same frame do not overlap, the readout states of different exposure units in the same frame do not overlap, and the output states of different exposure units in the same frame do not overlap; the exposure unit is a row or a column.
4. The control circuit of the image sensor according to claim 1, wherein In the global exposure mode, each frame sequentially experiences an exposure state, a pre-frame time, a readout state, and an output state; wherein, the exposure state of the next frame does not overlap with the pre-frame time of the previous frame, the readout states of different exposure units in the same frame do not overlap, and the output states of different exposure units in the same frame do not overlap; the exposure unit is a row or a column.
5. The control circuit of the image sensor according to claim 1, wherein The digital control circuit further includes: A register configuration module for configuring registers.
6. The control circuit of the image sensor according to claim 1, characterized in that, The digital control circuit further includes: A dark level automatic correction module for performing dark level correction.
7. The control circuit of the image sensor according to claim 1, wherein The analog circuit further includes: A phase-locked loop for generating a working clock according to a reference clock.
8. The control circuit of the image sensor according to claim 1, wherein The analog circuit further includes: A power-on reset module for performing power-on reset.
9. The control circuit of the image sensor according to claim 1, characterized in that, The analog circuit further includes: A temperature sensor for monitoring temperature.
10. An image sensor, characterized in that, A control circuit including the image sensor according to any one of claims 1 to 9.