CN111601054B

CN111601054B - Time sequence control method for novel drum-type exposure of image sensor

Info

Publication number: CN111601054B
Application number: CN202010414912.9A
Authority: CN
Inventors: 张正威; 张远; 李停; 陈西昌
Original assignee: Shanghai IC R&D Center Co Ltd; Chengdu Image Design Technology Co Ltd
Current assignee: Shanghai IC R&D Center Co Ltd; Chengdu Image Design Technology Co Ltd
Priority date: 2020-05-15
Filing date: 2020-05-15
Publication date: 2022-07-19
Anticipated expiration: 2040-05-15
Also published as: CN111601054A

Abstract

The invention provides a novel drum-type exposure time sequence control method for an image sensor, which comprises the following steps: the image sensor carries out N times of exposure on the same scene to obtain N times of exposure signals, and time parameters of the N times of exposure are mutually independent; generating a read enable signal; generating a timing gating signal; and the N state machines take the value of the time sequence gating signal as the enable respectively, and read the exposure signals for N times alternately and sequentially. By adopting N state machines, a time sequence control circuit and a time sequence gating signal for judging the relevance between the state machines, the reading of the exposure signals of N times is alternately and sequentially carried out when the novel drum-type exposure function of the N state machines is completed, the condition of read-out data superposition is avoided, and the CMOS image sensor can normally work. The degree of freedom of system configuration is increased, the multiplexing flexibility of the state machine is increased, and the structure of the state machine is simplified.

Description

Time sequence control method for novel drum-type exposure of image sensor

Technical Field

The invention belongs to the technical field of CMOS integrated circuits, and particularly relates to a novel drum-type exposure time sequence control method for an image sensor.

Background

As semiconductor process technology develops more and more mature, the advantages of low power consumption and high integration of CMOS image sensors become more and more obvious. A sensing device such as a photodiode in a CMOS image sensor generates charges from sensed photons by exposure to light, and then a readout circuit reads out the charges.

Conventional drum exposure modes are, for example: the exposure for the (i-1) th time, and then reading out the exposure signal for the (i-1) th time; then, the ith exposure is carried out, and then the ith exposure signal is read out; then, the (i + 1) th exposure is performed, and then the (i + 1) th exposure signal is read out, i.e., the exposure and the reading out of the image are interleaved. The adjacent number of readouts are separated by an exposure time, so that there is no overlap between successive, e.g. three, exposures, and there is no overlap between successive, e.g. three, readouts, which are performed sequentially in time.

In the conventional drum exposure, each column of pixels shares one set of reading circuit, when the reading circuit works normally, only one row of exposure signals (pixel data) can be read at one moment, and if the reading operation of the previous row of image signals is not finished, the next row of image signals enter the reading circuit, namely, the reading is overlapped, so that the CMOS image sensor cannot work normally.

In the novel drum-type exposure, time parameters of a plurality of continuous exposures are mutually independent, so that the plurality of exposures can be overlapped in time. And (3) overlapping images with different exposure time parameters for a plurality of times aiming at different bright and dark parts in a scene, and integrating to obtain a frame of image. The exposure of a plurality of times can overlap in time, and usually, the image exposure is read out after being completed every time, so that the situation that the reading is overlapped in time for a plurality of times can occur, as shown in fig. 1, the traditional drum-type exposure can only read out pixel data of one row at one moment, and the situation that the reading is overlapped in the same time margin in the novel drum-type exposure cannot be met, so that an analog circuit of the CMOS image sensor cannot correctly sample pixels, and the CMOS image sensor cannot normally work.

Disclosure of Invention

The invention aims to provide a novel drum-type exposure time sequence control method of an image sensor, which is characterized in that after the novel drum-type exposure is adopted, a plurality of times of reading of exposure signals are alternately and sequentially output, the condition of superposition of read data is avoided, and the CMOS image sensor is enabled to normally work.

The invention provides a novel drum-type exposure time sequence control method of an image sensor, which comprises the following steps:

a time sequence control method for novel drum-type exposure of an image sensor is characterized by comprising the following steps:

the method comprises the following steps that an image sensor carries out N times of exposure on the same scene to obtain N times of exposure signals, and time parameters of the N times of exposure are mutually independent;

generating a read enable signal, wherein the read enable signal is output in a pulse form, and the period is the row period of read data;

the time sequence control circuit generates a time sequence gating signal, and the period of the time sequence gating signal is the same as the row period of the read data;

and the N state machines take the value of the time sequence gating signal as enable respectively, and read the exposure signals for N times alternately and sequentially, wherein N is a natural number which is more than or equal to 2.

Further, the time parameters include an exposure start time, an exposure end time, and an exposure time length.

Furthermore, the time length of the N exposures is gradually reduced, and the photosensitive effective areas of the N exposure signals are the same in size.

Furthermore, instantiating the N state machines, and outputting the N times of exposure signals after the N times of exposure signals are selected by the time sequence gating signals.

Further, the time sequence gating signal is circulated in a period from 0 to N-1, when N state machines are read after being exposed in sequence, the data reading of the first state machine takes the '0' value of the time sequence gating signal as the enabling, the data reading of the second state machine takes the '1' value of the time sequence gating signal as the enabling, and so on, and the data reading of the Nth state machine takes the 'N-1' value of the time sequence gating signal as the enabling.

Further, the output length of the read enable signal is within the N read data time margins.

Further, the process of the state machine is as follows:

s1: the system is in an S _ IDLE state when not in operation, and the step S2 is executed after the exposure enabling signal is received; if the enable signal is not received, keeping in an S _ IDLE state;

s2: when the system is in the S _ EXPT exposure state, after the preset number of exposure lines is ended, go to step S3; if the preset exposure length is not finished, keeping in an S _ EXPT exposure state;

s3: when the system is in the S _ READ state, if a new exposure of the next frame is enabled, the process proceeds to step S4; if the timing strobe signal is received and the other state machines enter the read state, then go to step S5; if the system is stopped, that is, no new enable signal comes, the process goes to step S1 after the reading is finished; if the exposure enable signal is received after the preset read length is over, then the process goes to step S2; if no enable signal is received, keeping in an S _ READ reading state;

s4: if the timing strobe signal is received, the other state machines enter the read state, then go to step S5; if the current preset exposure length is finished, the step S3 is carried out; if the current preset exposure length is not finished, keeping in an S _ READ _ EXPT state;

s5: if the time sequence gating signal is received, namely when the current state machine effectively reads the enabling signal, the step S4 is executed when the current preset exposure length is not finished; if the preset exposure length is over, the step S3 is executed; if the preset readout length is over without receiving any enable signal, go to step S1; if no new enable signal is received, it remains in the S _ RD _ WAIT state.

Further, only one of the N exposure signals is read out at a time, and the remaining N-1 exposure signals are in a waiting state.

Further, there is no time interval or a certain time interval between two adjacent readings of the exposure signal.

Further, N equals 3.

Compared with the prior art, the invention has the following beneficial effects:

according to the novel drum-type exposure time sequence control method of the image sensor, the N state machines, the time sequence control circuit and the time sequence gating signals for judging the relevance among the state machines are adopted, when the novel drum-type exposure function of the plurality of state machines is finished, the N times of exposure signals are alternately and sequentially read, the condition that read data are overlapped is avoided, and the CMOS image sensor can normally work. The configuration freedom of the system is increased, the multiplexing flexibility of the state machine is increased, and the structure of the state machine is simplified.

Drawings

FIG. 1 is a schematic diagram of a new drum exposure of an image sensor with overlapped read data.

Fig. 2 is a flowchart illustrating a timing control method for a novel drum exposure of an image sensor according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of exposure and data readout in the novel drum-type exposure timing control method of the image sensor according to the embodiment of the invention.

Fig. 4 is a schematic diagram illustrating state transition of a state machine in a timing control method for a novel drum exposure of an image sensor according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of data readout in the timing control method of the novel drum exposure of the image sensor according to the embodiment of the invention.

Detailed Description

Based on the above research, the embodiment of the invention provides a novel time sequence control method for drum-type exposure of an image sensor. The invention is described in further detail below with reference to the figures and the specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It is to be noted, however, that the drawings are designed in a simplified form and are not to scale, but rather are to be construed in an illustrative and descriptive sense only and not for purposes of limitation.

The embodiment of the invention provides a novel drum-type exposure time sequence control method for an image sensor, as shown in fig. 2, comprising the following steps:

and the N state machines take the value of the time sequence gating signal as an enable respectively, and read the exposure signals for N times alternately and sequentially, wherein N is a natural number which is more than or equal to 2.

The image sensor is, for example, a CMOS image sensor, which generally adopts photodiode linear active pixels, and has a small dynamic response range which is far smaller than the dynamic range of 100 dB-120 dB of human eyes. When some scenes with a wide dynamic range are shot, because the brightness difference of the scenes far exceeds the tolerance of the photosensitive element, the obtained image hardly contains all details under a single imaging of a certain specified time length. For example, in a place with a dark brightness, the exposure may be insufficient, and in a bright area, the exposure may be overexposed, which makes it difficult to satisfy the requirement of obtaining image information in a large dynamic range. Therefore, in order to acquire a large dynamic range image, the image sensor performs N exposures on the same scene to acquire N exposure signals for different bright and dark parts in the scene, wherein time parameters of the N exposures are independent from each other, namely the start, the end and the exposure time length of each exposure are independent from each other. And carrying out exposure shooting twice or for multiple times on the same scene, respectively acquiring image information under different exposure conditions, and then realizing dynamic expansion through image fusion. The method is suitable for static scenes or relatively static scenes, namely, the target scene is unchanged or slightly changed during multiple exposure shooting. And (3) integrating and acquiring an image by overlapping the images with different exposure time parameters for N times.

The exposure time parameters comprise exposure start time, exposure end time and exposure time length, and the exposure time length is equal to the exposure end time minus the exposure start time. The short exposure is used for obtaining the brighter pixels, the long exposure is used for obtaining the darker pixels, and the multiple combination is used for overcoming the defect that all details cannot be displayed in a single imaging process. Illustratively, the time length of the N times of exposure is gradually reduced, and the photosensitive effective areas of the N times of exposure signals are the same in size.

As shown in fig. 3, taking N as an example, for the new drum exposure method, three exposures are performed sequentially (i.e., first, second, and third) and the corresponding data read is a whole frame, the time length of the three exposures gradually decreases, for example, expt _1> expt _2> expt _3, the photosensitive effective areas of the three exposure signals have the same size, that is, the data length of the three exposures is the size of the photosensitive effective area of the entire image sensor, and accordingly, the time lengths of the three read states are also the same.

As shown in fig. 4 and 5, a read enable signal read _ enable is generated in coordination with data reading, and this signal is output in the form of a pulse with a period of the line period length of the read data.

A timing strobe signal sel _ num matched with read data is generated, the length of the sel _ num signal coincides with a row period of read data, and the output length is within three read data time margins.

And in the time margin of one row, when the three-frame image is read out after exposure, the three state machines respectively use the value of the time sequence strobe signal sel _ num as the enabling, and the read data are alternately and sequentially output.

In the exposure phase, the pixel circuit of the CMOS image sensor performs an exposure operation, generating photo-generated charges. An amplification and quantization processing circuit of the CMOS image sensor amplifies and quantizes photo-generated charges output by a pixel circuit. The readout circuit of the CMOS image sensor performs a readout (transfer) operation on the signal output from the amplification quantization processing circuit.

The present embodiment uses three identical state machines to perform sequencing control on the read data. A state machine defines a plurality of states and transitions between the states. The state machine operates in response to a series of events that, when satisfied by certain trigger conditions, cause the state machine to migrate from a current state to a next state. Among the plurality of states defined, there is at least one initial state and at least one final state, the state machine starting to run from the initial state and stopping when transitioning to the final state.

A timing strobe signal sel _ num matched with read data is generated, the length of the sel _ num signal coincides with a row period of the read data, and the output length is within three read data time margins, cycling at periods of 0, 1, and 2.

When the three state machines are read out after sequential exposures, the first state machine data readout is enabled with the "0" value of the sel _ num signal, the second state machine data readout is enabled with the "1" value of the sel _ num signal, and the third state machine data readout is enabled with the "2" value of the sel _ num signal. The non-sampled corresponding value jumps to the S _ RD _ WAIT state when a new strobe signal arrives.

As shown in fig. 4, the state machine state transitions are schematic.

s2: when the system is in the S _ EXPT exposure state, after the preset number of exposure lines is finished, go to step S3; if the preset exposure length is not finished, keeping in an S _ EXPT exposure state;

s4: if the timing strobe signal is received and the other state machines enter the read state, then step S5 is entered; if the current preset exposure length is finished, the step S3 is carried out; if the current preset exposure length is not finished, keeping in an S _ READ _ EXPT state;

s5: if the time sequence gating signal is received, namely when the current state machine effectively reads the enabling signal, the step S4 is executed when the current preset exposure length is not finished; if the preset exposure length is over, the process goes to step S3; if the preset readout length is over and no enable signal is received, then go to step S1; if no new enable signal is received, it remains in the S _ RD _ WAIT state.

As shown in fig. 4 and 5, during the switching between steps S5 and S3, or between steps S5 and S4, a read enable signal read _ enable matched with data read is first generated, which is output in the form of a pulse with a period of the line period length of the read data, and then a timing strobe signal sel _ num matched with read data is generated, which has a length identical to the line period of the read data and an output length of 0, 1, and 2 cycles within three read data time margins; when the three state machines are read out after exposure in sequence, the first state machine data readout is enabled by the value of '0' of the sel _ num signal, the second state machine data readout is enabled by the value of '1' of the sel _ num signal, and the third state machine data readout is enabled by the value of '2' of the sel _ num signal; the non-sampled corresponding value jumps to the S _ RD _ WAIT state when a new strobe signal arrives.

In fig. 5, a preferred state is shown, after the i-1 th exposure signal is read out, the i-th exposure signal is read out immediately, and then the i +1 th exposure signal is read out immediately, there is no time interval between the three successive exposure signal readings, and the signals are seamlessly butted; it should be understood that, with the idea that the exposure signals (pixel data) are read out only once at a time, the read-out data do not overlap, and a time interval between adjacent times of exposure signal read-out is also allowed, which is set according to actual requirements. For example, after the i-1 th exposure signal readout, the i-th exposure signal readout is performed with a certain time interval.

In one period, three state machines are instantiated, three paths of read data after exposure are selected by a time sequence gating signal and then output, the read data are alternately and sequentially output to the analog circuit for partial sampling processing, and meanwhile, the read data are in a current unread state and enter a read and wait state.

The method adopts a plurality of state machines, a time sequence control circuit and a gating enable signal for judging the relevance between the state machines, and when the novel drum-type exposure function of the plurality of state machines is completed, read data are alternately and sequentially output, the degree of freedom of system configuration is increased, the multiplexing flexibility of the state machines is increased, and the structure of the state machines is simplified. The scheme provides a logic implementation of a novel drum-type exposure time sequence control method applied to an image sensor, and belongs to the circuit design of chip hardware.

The novel drum-type exposure mode is a soft and hard solution of the image sensor in solving a wide dynamic range, meets and well processes special processing requirements of read data for hardware, achieves improvement of flexibility of the solution in multiplexing, and is a main aspect that a digital part of a circuit needs to be well held and controlled.

The invention also provides a computer storage medium which comprises a computer program, and the computer program runs the novel roller type exposure time sequence control method of the image sensor to control the reading of the exposure signal.

Those of ordinary skill in the art will understand that: all or a portion of the steps of implementing the above-described method embodiments may be performed by hardware associated with program instructions. The aforementioned program may be stored in a computer (processor) -readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.

In summary, in the novel drum exposure mode, the readout timing data output by the digital circuit part after exposure is provided to the analog circuit for sampling, which requires that the readout data after three exposures can be acquired and the effective readout data does not overlap. In order to meet the requirements of the circuits, the embodiment of the invention provides a novel drum-type exposure time sequence control method for an image sensor, which instantiates three state machines, and three paths of read data after exposure are selected by using a time sequence gating signal and then output, so that the read data are alternately output to an analog circuit part for sampling processing, and simultaneously, the read data enter a read and wait state in a current unread state.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the method disclosed by the embodiment, the description is relatively simple because the method corresponds to the device disclosed by the embodiment, and the relevant points can be referred to the description of the method part.

The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.

Claims

1. A time sequence control method for novel drum-type exposure of an image sensor is characterized by comprising the following steps:

the N state machines take the value of the time sequence gating signal as enabling respectively, reading of the exposure signals for N times is carried out alternately and sequentially, and N is a natural number which is more than or equal to 2;

instantiating the N state machines, and outputting the N times of exposure signals after the N times of exposure signals are selected by the time sequence gating signals; and reading data are alternately and sequentially output when the N state machines have a drum-type exposure function by adopting the N state machines, the time sequence control circuit and the time sequence gating signal for judging the relevance among the state machines.

2. The timing control method of a novel drum-type exposure of an image sensor as claimed in claim 1, wherein said time parameters include an exposure start time, an exposure end time and an exposure time length.

3. The method as claimed in claim 2, wherein the time length of the N exposures is gradually reduced, and the size of the photosensitive effective area of the N exposure signals is the same.

4. The method as claimed in claim 1, wherein the timing strobe signal is cycled between 0 and N-1, when N state machines are sequentially exposed and then read out, the first state machine data read out is enabled by the "0" value of the timing strobe signal, the second state machine data read out is enabled by the "1" value of the timing strobe signal, and so on, the nth state machine data read out is enabled by the "N-1" value of the timing strobe signal.

5. The timing control method of a new drum exposure of an image sensor as claimed in claim 1, wherein an output length of said read enable signal is within said N read-out data time margins.

6. The method for controlling the timing of a novel drum-type exposure of an image sensor according to any one of claims 1 to 5, wherein the state machine process comprises:

s3: when the system is in the S _ READ state, if a new exposure of the next frame is enabled, the process proceeds to step S4; if the timing strobe signal is received, the other state machines enter the read state, then go to step S5; if the system is stopped, that is, no new enable signal comes, the process goes to step S1 after the reading is finished; if the exposure enable signal is received after the preset read length is over, then the process goes to step S2; if no enable signal is received, keeping in an S _ READ reading state;

7. The timing control method of novel drum-type exposure of image sensor as claimed in any one of claims 1 to 5, wherein only one of said N exposure signals is read out at a time, and the remaining N-1 exposure signals are in a waiting state.

8. The method as claimed in any of claims 1 to 5, wherein there is no time interval or a certain time interval between two adjacent readings of the exposure signal.

9. The timing control method of a novel drum exposure of an image sensor according to any one of claims 1 to 5, wherein N is equal to 3.