CN106303307B - Imaging sensor and its control method - Google Patents

Abstract

The invention discloses a method for controlling an image sensor, which is characterized by comprising the following steps: S1, controlling the pixels of the image sensor to perform long integration and short integration; and S2, performing any three primary color values in the long integration of the pixels When saturated, the actual size of the saturated primary color value is calculated by the ratio of the primary color value between the unsaturated primary color value and the short-integrated primary color value. The present invention also provides an image sensor. Therefore, the image sensor and the control method thereof according to the embodiments of the present invention can improve the dynamic range while avoiding the increase of dark current and the increase of noise.

Description

Image sensor and control method thereof

technical field

The present invention relates to imaging technology, in particular to an image sensor and a control method thereof.

Background technique

A complementary metal-oxide semiconductor (CMOS) image sensor includes a pixel array, a control circuit, an analog front-end processing circuit, an A/D converter, an image signal processing circuit, and related memories. With the development of CMOS image sensors, the pixel size is getting smaller and smaller, but the dynamic range of the smaller size pixel is limited by the saturated electron capacity of the photodiode.

The prior art mainly improves the photocharge capacity of the photodiode by increasing the implantation energy and implantation dose of the N-type ions, thereby improving the photosensitive capability of the photodiode; or increasing the depth of the photodiode to increase the photodiode's ability to collect electrons. The charge holding capacity of the photodiode improves the photodiode's photosensitive capacity.

However, increasing the implantation energy and implantation dose of PDN ions to improve the charge holding capacity of the photodiode will increase the pinned voltage of the photodiode, and in addition, the dark current is too large. The implantation of large dose and high energy increases lattice damage, etc., resulting in increased dark current and increased noise.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the present invention needs to provide an image sensor and a control method thereof.

The image sensor of the embodiment of the present invention includes:

pixel array;

a controller, configured to control the pixel short integral of the pixel array to obtain the ratio of primary color values among the three primary color values, and the controller is further configured to control the pixel long integral;

The processor is configured to calculate the actual size of the saturated primary color value according to the unsaturated primary color value of the pixel long integral and the ratio of the primary color value when any one of the three primary color values of the pixel long integral is saturated.

In some embodiments, the processor includes:

a judgment unit for judging whether any of the three primary color values of the pixel long integral is saturated; and

The calculating unit is configured to calculate the ratio of the primary color values when any one of the three primary color values is saturated, and calculate the actual size of the saturated primary color value according to the unsaturated primary color value and the ratio of the primary color values.

In some embodiments, the determination unit is further configured to notify the calculation unit to skip the calculation of the pixel when none of the three primary color values of the pixel is saturated.

In some embodiments, the controller is further configured to control the pixel array to read out the integral data row by row; the image sensor further includes a memory; the memory includes multiple rows of storage units; each row of the storage units uses is used to store one row of the integration data; the controller is used to control the pixel array to perform long integration row by row and to read out the long integration data row by row, and the controller is used to sequentially store the long integration data in the odd rows of the After the storage unit, control the pixel array to reset to start short integration, and the controller is further configured to control the pixel array to read out the short integration data row by row when reading out the long integration data of the kth row, and the controller is configured to read out the short integration data row by row. The short integration data are sequentially stored in the storage cells of the even rows.

The control method of the image sensor according to the embodiment of the present invention includes the following steps:

S1, controlling the pixels of the image sensor to perform long integration and short integration;

S2, when any three primary color values of the pixel long integral are saturated, the actual value of the saturated primary color value is calculated by the ratio of the primary color value between the unsaturated primary color value of the pixel long integral and the three primary color values of the pixel short integral size.

In some embodiments, the step S2 includes:

S21: Determine whether any of the three primary color values of the pixel long integral is saturated; and

S22: Calculate the primary color value ratio when any of the three primary color values is saturated, and calculate the actual size of the saturated primary color value according to the unsaturated primary color value and the primary color value ratio.

In some embodiments, the step S2 includes:

When none of the three primary color values of the pixel is saturated, the calculation unit of the image sensor is notified to skip the calculation of the pixel.

In some embodiments, the step S1 includes:

Control the pixel array of the image sensor to perform long integration line by line and read out the long integration data line by line, store the long integration data in sequence in the storage units of odd rows of the memory of the image sensor, and then control the pixel array Reset starts short integration, and controls the pixel array to read out short integration data row by row when reading out long integration data of the kth row, and sequentially stores the short integration data in the storage cells of even rows.

The image sensor and the control method thereof according to the embodiments of the present invention improve the dynamic range while avoiding the increase of dark current and the increase of noise.

Additional aspects and advantages of the present invention will be set forth, in part, from the following description, and in part will be apparent from the following description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of functional modules of an image sensor according to an embodiment of the present invention.

FIG. 2 is a working principle diagram of an image sensor according to an embodiment of the present invention.

FIG. 3 is another working principle diagram of the image sensor according to an embodiment of the present invention.

FIG. 4 is a schematic flowchart of a control method of an image sensor according to an embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " Or The positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it should not be construed as a limitation of the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined as "first", "second" may expressly or implicitly include one or more of said features. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; it can be mechanical connection, electrical connection or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction of two elements relation. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may include the first and second features in direct contact, or may include the first and second features Not directly but through additional features between them. Also, the first feature being "above", "over" and "over" a second feature includes the first feature being directly above and obliquely above the second feature, or simply denoting that the first feature is level above the second feature. The first feature is "below", "beneath" and "beneath" the second feature includes the first feature being directly above and diagonally above the second feature, or simply means that the first feature is level less than the second feature.

The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are only examples and are not intended to limit the invention. Furthermore, the present disclosure may repeat reference numerals and/or reference letters in different instances for the purpose of simplicity and clarity and not in itself indicative of a relationship between the various embodiments and/or arrangements discussed. In addition, the present disclosure provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.

Referring to FIG. 1 , an image sensor 100 according to an embodiment of the present invention includes a pixel array 10 , a controller 20 and a processor 30 . The controller 20 is used to control the short integration of the pixels 11 of the pixel array 10 to obtain the ratio of the primary color values among the three primary color values, and the controller 20 is also used to control the long integration of the pixels 11 . The processor 30 is configured to calculate the actual size of the saturated primary color value by using the unsaturated primary color value and the ratio of the primary color value when any three primary color values of the long integral of the pixel 11 are saturated.

In this embodiment, the pixel array 10 has a Bayer structure, that is, red pixels (with a red bandpass filter, so that only red light can pass through and be sensed) 11r, green pixels (with a green bandpass filter) 11r A light sheet so that only green light can pass through and be sensed) 11gb, 11gr and blue pixels (with a blue bandpass filter, so that only blue light can pass through and be sensed) 11b constitute the Bayer unit 12 . The pixel value (color value) of each pixel 11r, 11gb, 11gr or 11b in the Bayer unit 12 is represented by three primary color values (according to color theory, each color value can be decomposed into red, green and blue three primary color values, namely It can be represented by the three primary color values of red, green and blue), that is, the red value R (that is, the pixel value of the red pixel 11r), the green value G (that is, the average value of the pixel values of the green pixels 11gb and 11gr), and the blue value B (that is, the blue value pixel value of the color pixel 11b).

That is, in the present embodiment, the three primary colors are the optical three primary colors (RGB). Of course, in other embodiments, the three primary colors may also be printing three primary colors (complementary colors of the optical three primary colors): cyan (C), magenta (M), and yellow (Y).

Please also refer to FIG. 2 , the controller 20 can control the charge integration time (for example, the exposure time T) of each pixel 11r, 11gb, 11gr or 11b of the pixel array 10 through the exposure time T so as to determine each pixel 11r, 11gb , 11gr or 11b of the three primary color values R, G, B. However, in the actual use process, the contrast between light and dark in some scenes is too strong, so that in order to obtain the characteristics of some dark parts, a longer exposure time T needs to be used, and in this case, the dynamic range of the pixel array 10 itself is limited. , some primary color values of some bright parts may be overexposed, beyond the dynamic range of the pixel array 10. For example, as shown in FIG. 2, after the integration time (which is the exposure time T), the green pixels 11gb, 11gr and blue The color pixel 11b is overexposed (charge overflow) and cannot represent the real primary color values G and B of each pixel 11r, 11gb, 11gr or 11b.

However, for each pixel 11r, 11gb, 11gr or 11b, the color value is fixed for a certain period of time, that is, the ratio of the three primary color values (ie R:G:B, called the ratio of primary color values) is Fixed, so the ratio of primary color values does not change throughout the integration process.

In this way, a short integral of each pixel 11r, 11gb, 11gr or 11b can be used to obtain the primary color value ratio (the integration time is much shorter than the exposure time T, at this time each pixel 11r, 11gb, 11gr or 11b will not be overexposed, so , the ratio of primary color values is true), then, if any of the primary color values R, G, and B are saturated during long integration, the actual size of the saturated primary color value is calculated by the unsaturated primary color value and the primary color value ratio.

For example, in Figure 2, the three primary color values R', G', B' can be obtained by short integration (the integration time T' is much shorter than the exposure time T), and thus the primary color value ratio R':G':B' can be obtained. In the case of long integration (the integration time is the exposure time T), the primary color values G and B are saturated, that is, the green pixels 11gb and 11gr and the blue pixel 11b are overexposed. However, the actual size of the primary color values G and B can be calculated as follows:

G=(G'*R)/R'; and

B=(B'*R)/R'.

Therefore, the image sensor 10 according to the embodiment of the present invention does not improve the dynamic range of the pixel array by increasing the implantation energy and implantation dose of N-type ions to improve the photocharge holding capacity of the photodiode, thereby avoiding the increase of dark current and the increase of noise.

In this embodiment, the processor includes a judgment unit 31 and a calculation unit 32 . The judging unit 31 is used to judge whether any of the three primary color values R, G and B of the long integral are saturated. The calculation unit 32 is used to calculate the primary color value ratio R':G':B' when any of the three primary color values R, G, B is saturated, and calculate the saturation according to the unsaturated primary color value and the primary color value ratio R':G':B' The actual size of the primary color value.

Please refer to FIG. 3, for some dark part pixels 11r, 11gb, 11gr or 11b, during long integration, the three primary color values R, G, B are not saturated, therefore, no calculation is required, so, the judgment unit 31 first judges and then informs the calculation The unit 32 omits the calculation of the ratio of the primary color value of the pixel 11r, 11gb, 11gr or 11b, which can reduce the amount of calculation.

The controller 10 is also used to control the pixel array 10 to read out the integrated data row by row (ie, the pixel values of the entire row). The image sensor 10 also includes a memory 40 . The memory 40 is divided into rows of memory cells, eg, ten rows of memory cells 41-4a. Each row of memory cells is used to store (cache) one row of integral data.

In this embodiment, the controller 20 controls the pixel array 10 to perform long integration row by row and read out the integrated data row by row, store the integrated data in the odd row storage units in turn, reset to perform short integration, and read out the integrated data row by row when reading out the integrated data of k rows The short integration data are sequentially stored in the even row memory cells. Reset refers to clearing the charge of the pixel (k is a natural number).

For example, taking k=4 as an example, at the beginning of exposure, the controller 20 controls the first row to the Nth row of the pixel array 10 (N is the total number of rows of the pixel array 10, and the time interval of each row is t). , and read out the long integration data of the first line (that is, exposure time T=(n-1)*t) when the long integration starts in the nth line (n is a natural number, generally tens or hundreds), and then the first line The row is reset for short integration; when the n+1th row starts long integration, the long integration data of the second row is read out, and then the second row is reset for short integration, and so on.

After reading out the long integration data 4 of the fourth row (k=4) and storing it in the storage unit 41, read out the short integration data 1' of the first row and store it in the storage unit 42; after reading out the long integration data of the fifth row After the data 5 is stored in the storage unit 42, the short integration data 2' of the second row is read out, and so on, until the long integration data 8 of the eighth row is read out and stored in the storage unit 49, and then the short integration data of the fifth row is read out. After data 5', the memory 40 is full. The long integration data 9 of the ninth row is read out and stored in the storage unit 1 and the short integration data 6' of the sixth row is stored in the storage unit 42, starting a new cycle. The long integral data 4 of the fourth row and the short integral data 1' of the first row have been read out to the processor 30 for processing, such as judgment or calculation.

In this way, when the pixels in the following row are used for long integration, the front row after the completion of the long integration can be used for short integration, thereby making the entire exposure process more compact. In addition, the utilization rate of the memory 40 can also be improved.

Referring to FIG. 4 , the control method of the image sensor according to the embodiment of the present invention includes:

S1, control the pixel 11r, 11gb, 11gr or 11b to perform long integration and short integration;

S2, when any of the three primary color values R, G, B of the long integral of the pixel 11r, 11gb, 11gr or 11b is saturated, pass the unsaturated primary color value R, G or B and the three primary color values of the short integral R', G', B' The ratio between the primary color values R':G':B' to calculate the actual size of the saturated primary color value.

In some embodiments, step S2 includes:

S21: Determine whether any three primary color values R, G, B of the long integral of the pixel 11r, 11gb, 11gr or 11b are saturated; and

S22: When any three primary color values are saturated, calculate the primary color value ratios R', G', B', and calculate the actual size of the saturated primary color value according to the unsaturated primary color value and the primary color value ratio.

In some embodiments, step S2 includes:

When none of the three primary color values R, G, and B of the pixel are saturated, the calculation unit 32 is notified to skip the calculation of the pixel 11r, 11gb, 11gr or 11b.

In some embodiments, step S1 includes:

Control the pixel array 10 to perform long integration row by row and read out the long integration data row by row, store the data in odd rows of the memory 40 in turn, and then reset to start short integration, and read out the short integration row by row when reading out the long integration data of the kth row. Data is sequentially stored in the even-numbered row locations of the memory 40 .

In the description of this specification, reference to the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" or the like is intended to incorporate the A particular feature, structure, material, or characteristic described by an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, The scope of the invention is defined by the claims and their equivalents.

Claims (8)

1. an image sensor, is characterized in that, comprises: pixel array; a controller, configured to control the pixel short integral of the pixel array to obtain the ratio of primary color values among the three primary color values, and the controller is further configured to control the pixel long integral; The processor is configured to calculate the actual size of the saturated primary color value according to the unsaturated primary color value of the pixel long integral and the ratio of the primary color value when any one of the three primary color values of the pixel long integral is saturated. 2. The image sensor of claim 1, wherein the processor comprises: a judgment unit for judging whether any of the three primary color values of the pixel long integral is saturated; and The calculating unit is configured to calculate the ratio of the primary color values when any one of the three primary color values is saturated, and calculate the actual size of the saturated primary color value according to the unsaturated primary color value and the ratio of the primary color values. 3 . The image sensor according to claim 2 , wherein the determination unit is further configured to notify the calculation unit to skip the calculation of the pixel when none of the three primary color values of the pixel is saturated. 4 . 4. The image sensor according to claim 1, wherein the controller is further configured to control the pixel array to read out the integral data row by row; the image sensor further comprises a memory; the memory comprises a multi-line storage Each row of the storage unit is used to store one row of the integral data; the controller is used to control the pixel array to perform long integration row by row and read out the long integral data row by row, and the controller is used to store the long integral data row by row. After the data is sequentially stored in the storage units of odd rows, it controls the pixel array to reset and start short integration, and the controller is further configured to control the pixel array to read out short integration data row by row when reading out the long integration data of the kth row. Integration data, the controller is configured to store the short integration data in the storage units of the even rows in sequence. 5. A control method for an image sensor, comprising the following steps: S1, controlling the pixels of the image sensor to perform long integration and short integration; and S2, when any three primary color values of the pixel long integral are saturated, the actual value of the saturated primary color value is calculated by the ratio of the primary color value between the unsaturated primary color value of the pixel long integral and the three primary color values of the pixel short integral size. 6. The control method of an image sensor according to claim 5, wherein the step S2 comprises: S21: Determine whether any of the three primary color values of the pixel long integral is saturated; and S22: Calculate the primary color value ratio when any of the three primary color values is saturated, and calculate the actual size of the saturated primary color value according to the unsaturated primary color value and the primary color value ratio. 7. The control method of an image sensor according to claim 6, wherein the step S2 comprises: When none of the three primary color values of the pixel is saturated, the calculation unit of the image sensor is notified to skip the calculation of the pixel. 8. The control method of an image sensor according to claim 6, wherein the step S1 comprises: Control the pixel array of the image sensor to perform long integration line by line and read out the long integration data line by line, store the long integration data in sequence in the storage units of odd rows of the memory of the image sensor, and then control the pixel array Resetting starts short integration, and the pixel array is controlled to read out short integration data row by row when reading out the long integration data of the kth row, and store the short integration data in the storage cells of even rows in sequence.