Phase detection focusing method, imaging system, image sensor and terminal

Abstract

The invention discloses a phase detection focusing method, an imaging system, an image sensor and a terminal, relates to the field of phase detection automatic focusing, and solves the problems that when an image sensor adopting a correlated double-sampling technology reads a pixel charge quantity, the first part pixel charge quantity and the second part pixel charge quantity have deviation, and the image sensor is not accurate in focusing. And the purpose of phase detection automatic focusing cannot be achieved, so that the focusing precision of an imaging process is influenced. According to the technical scheme, the method is characterized in that the analog-to-digital conversion process of the first part pixel charge quantity of an exposure processing area is adjusted according to a feedback coefficient generated in an exposure multiplication area, so that the first part pixel charge quantity read from the exposure processing area is equal to the second part pixel charge quantity, and phase focusing is completed. According to the invention, there is no deviation between the first part pixel charge quantity and the second part pixel charge quantity read out from the exposure processing area, the purpose of phase detection automatic focusing is achieved, and the focusing precision of the imaging process is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of phase detection auto-focusing, more particularly, it relates to a phase detection focusing method, an imaging system, an image sensor and a terminal. BACKGROUND

[0002] With the popularization of phase detection auto-focusing technology PDAF, in the common three types of PDAF (shield pixel, 2x1 on chip lens (2x1 OCL), full pixel dual core focusing (Dual PD)), 2x1 OCL and Dual PD both belong to dual core system, and both will go through twice pixel charge reading process (i.e. the way of opening TG (Transfer Gate) transmission gate twice to read pixel charge amount in pixel photoelectric conversion, to distinguish the first part of pixels and the second part of pixels).

[0003] And the image sensor equipped with CDS (Correlated Double Sampling) technology will keep accumulating charge state before the TG (Transfer Gate) is opened when sampling the signal, resulting in a certain deviation between the actual read second part of pixel charge amount and the ideal state, so that the first part of pixel charge amount and the second part of pixel charge amount are not equal, and the purpose of phase detection auto-focusing is not achieved, thereby affecting the focusing effect. SUMMARY

[0004] The purpose of the present application is to provide a phase detection focusing method, an imaging system, an image sensor and a terminal, which solves the problem that when the image sensor using the correlated double sampling technology reads a pixel charge amount, the first part of pixel charge amount and the second part of pixel charge amount will deviate, which cannot achieve the purpose of phase detection auto-focusing, thereby affecting the focusing accuracy of the imaging process.

[0005] The above technical purpose of the present application is realized by the following technical scheme: The first aspect of the present application provides a phase detection focusing method applied to an image sensor using a correlated double sampling technology, the method comprising: adjusting the analog-digital conversion process of the first part of pixel charge amount of the exposure processing area according to the feedback coefficient generated in the exposure multiplication area, so that the first part of pixel charge amount and the second part of pixel charge amount read out from the exposure processing area are equal, and the phase focusing is completed.

[0006] In an implementation scheme, the feedback coefficient generated in the exposure multiplication area is specifically: determining the exposure time and interval time required for reading the first part of pixel charge amount and the second part of pixel charge amount of the exposure multiplication area; a proportionality coefficient of phase focus is calculated according to the exposure time and the interval time; The proportionality coefficient is multiplied by a preset conversion coefficient, an analog signal quantity and a digital signal quantity to obtain a feedback coefficient; wherein the conversion coefficient refers to a bias in an analog-digital conversion or digital-analog conversion process.

[0007] In an implementation, the interval time is a time difference between two times when a transfer gate connected to the photodiode of the first part of pixels is opened.

[0008] In an implementation, a proportionality coefficient of phase focus is calculated according to the exposure time and the interval time, specifically: a reading time for reading the first part of pixel charge quantity is obtained according to a difference between the exposure time and the interval time; a proportionality coefficient of phase focus is obtained according to a ratio between the exposure time and the reading time.

[0009] In an implementation, the conversion coefficient is 1.

[0010] In an implementation, the proportionality coefficient is multiplied by a preset conversion coefficient, an analog signal quantity and a digital signal quantity, and the multiplication expression is: ; wherein, a represents the feedback coefficient, DAC represents an analog signal quantity processed by a digital-analog converter, ADC represents a digital signal quantity processed by an analog-digital converter, T represents the exposure time, represents the interval time.

[0011] In an implementation, an analog-digital conversion process of the first part of pixel charge quantity in the exposure processing area is adjusted, specifically: the feedback coefficient is converted into an analog signal; a starting position of a slope voltage of an analog converter used for reading the first part of pixel charge quantity is raised according to a value of the analog signal, so as to increase a counting time for reading the first part of pixel charge quantity, and compensation of the first part of pixel charge quantity is completed.

[0012] In a second aspect of the present application, a pattern sensor using a correlated double sampling technology is provided, which is used to execute a phase detection focus method provided in the first aspect of the present application.

[0013] In a third aspect of the present application, a phase detection focus imaging system is provided, which comprises: a pattern sensor using a correlated double sampling technology provided in the second aspect of the present application; and An application processor is configured to process pixel data output by the correlated double sampling (CDS) image sensor to generate an image.

[0014] In a fourth aspect, the present application provides a terminal comprising the phase detection focusing imaging system according to the third aspect.

[0015] Compared with the prior art, the present application has the following advantages: In the phase detection focusing method, the imaging system, the image sensor and the terminal, a feedback coefficient for compensating the first part of pixels in the exposure processing area is generated in the exposure multiplication area of the imaging area of the image sensor, and the reading voltage of the analog-digital conversion circuit is biased and adjusted based on the feedback coefficient, so that the exposure amount of the first part of pixels in the exposure processing area is compensated, the first part of pixel charge and the second part of pixel charge read out from the exposure processing area are not deviated, and the purpose of phase detection automatic focusing is achieved, and the focusing accuracy of the imaging process is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In the drawings: Figure 1 A principle block diagram of the phase detection focusing imaging system provided by the embodiments of the present application; Figure 2 A phase focusing principle diagram provided by the prior art; Figure 3 A pixel circuit principle diagram provided by the prior art; Figure 4 A charge accumulation example diagram of the first part of pixels and the second part of pixels provided by the prior art; Figure 5 A sampling example diagram of pixel charge provided by the correlated double sampling technology of the prior art; Figure 6 A reading example diagram of pixel charge provided by the correlated double sampling technology of the prior art; Figure 7 A feedback system example diagram of the phase detection focusing imaging system provided by the embodiments of the present application; Figure 8 A pixel area diagram of the image sensor provided by the prior art; Figure 9 A pixel charge reading example diagram of the correlated double sampling provided by the prior art; Figure 10 A pixel charge reading example diagram of the correlated double sampling provided by the embodiments of the present application.

[0017] Reference signs and drawing description: S01, pixel array; S02, analog circuit; S03, digital circuit; S04, feedback system; S05, firmware; S06, application processor; S12, ADC; S13, digital signal processing unit; S14, feedback coefficient; S15, DAC; S16, exposure multiplication region; S17, exposure processing region. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be given to the present application in combination with embodiments and drawings, the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application.

[0019] It should be noted that the term “include” or “may include” used in various embodiments of the present application indicates the existence of the claimed function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present application, the terms “include”, “have” and their synonyms only mean to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing, and should not be understood as first excluding the existence or addition of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing.

[0020] It should be understood that terms such as “first”, “second” are only used for description purposes, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with “first”, “second” can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of “a plurality of” is two or more, unless otherwise specifically limited.

[0021] The embodiment of the present application provides a phase detection focusing method, which is applied to an image sensor using correlated double sampling technology, for example, the image sensor can be a CCD image sensor, a CMOS image sensor, etc. The phase detection focusing method comprises: according to the feedback coefficient generated in the exposure multiplication region, adjusting the analog-to-digital conversion process of the first part of the pixel charge quantity of the exposure processing region, so that the first part of the pixel charge quantity read out from the exposure processing region is equal to the second part of the pixel charge quantity, and the phase focusing is completed.

[0022] Specifically, first introduce the focusing principle of phase detection auto focus (PDAF), such as Figure 2S07-S09, the offset and phase difference information of the focus is determined according to the distance and change between the pixel points, and the current lens position is determined to be the position of the in-focus state with the sharpest phase, that is Figure 2 The phase difference is zero, and the focus state (S08) is shown, so that the vector of the lens should be moved, and secondly, since the PDAF is a general technology, the explanation of the under-focus state shown in S07 and the over-focus state shown in S09 is omitted. In order to realize the above-mentioned focusing function, the image sensor needs to support PDAF (phase detection auto focus function), and secondly, the camera needs to calibrate the phase data at different distances, and the data mainly needs to contain the corresponding relationship between the phase difference and the object distance. By adjusting the lens, the phase difference information can be obtained, and the phase difference information is obtained according to the internal calibration data, and the direction and distance of the lens to be moved are calculated, which greatly improves the focusing speed.

[0023] Secondly, the light signal sampling process of the image sensor is introduced, as shown in Figure 3 Firstly, pixel exposure (signal accumulation) is carried out, TG (transfer gate) / Reset (reset) / Select (selector) is turned off, PD (photo diode) receives light source, photoelectric conversion is carried out, and photoelectrons are accumulated; then Select and Reset transistors are turned on, reset is carried out, and after reset is completed, Reset transistor is turned off again; finally, TG is turned on, photoelectrons in PD are transferred to FD (floating diffusion region), and then TG is turned off again to avoid the influence of subsequent photoelectric conversion in PD on FD (floating diffusion region); at the same time, voltage is generated due to the reception of photoelectrons by FD, and the switch is controlled to transmit the signal out.

[0024] According to the photoelectric conversion principle of the image sensor and the related double sampling principle of phase focusing driving, the typical phase focusing mode of the image sensor is taken as an example (analogy 2x1OCL and Dual PD dual-core system), and the rest of the phase focusing modes are applicable.

[0025] The pixel sampling process of the image sensor is explained: as shown in Figure 4 A phase focusing pixel point is divided into two parts, and each part is configured with a PD structure for photoelectric conversion; firstly, the charge amount S10 of the first part pixel (PD1) is read out; after reading out the electrical signal amount of the first part pixel, the second part pixel (PD2) of the same pixel point is read out, and at this time, the charge amount S10 of the first part pixel and the sum S11 of the charge amounts of the first part pixel and the second part pixel can be obtained through two times of signal reading.

[0026] S10: For the same phase focusing pixel, the charge amount accumulated by the first part pixel.

[0027] S11: For the same phase-focused pixels, the total charge accumulated in the first part of the pixels and the second part of the pixels.

[0028] As can be seen from the principle of phase detection autofocus, to achieve... Figure 2 In the focus state where the recorded phase difference is zero (S08), the charge amounts of the two parts of the same pixel corresponding to the phase-focused pixel point must be kept at the same level. However, due to the pixel reading order involved in phase focusing, the total charge accumulated by the first part of the pixel plus the second part of the pixel (S11) - the charge amount of the first part of the pixel (S10) ≠ the charge amount of the second part of the pixel. In other words, the charge amounts accumulated and read by PD1 and PD2 are different.

[0029] The reason for the above problem is that when reading pixels using CDS technology, it is necessary to first read the charge of the first part of the pixels (S10). This involves opening the TG (transmission gate) of the photodiode connected to the first part of the pixels to complete the reading of the charge of the first part of the pixels. Next, to further read the total charge of the first part of the pixels and the second part of the pixels (S11), it is necessary to simultaneously open the TG of the photodiodes connected to the first part of the pixels and the second part of the pixels. For the first part of the pixels, the photodiode, which should have been read in one operation, accumulates additional charge during the interval between the two TG openings, and this additional charge is newly accumulated after the charge of the first part of the pixels has been read. Therefore, after the total charge of the first part of the pixels plus the second part of the pixels (S11) is read, due to this additional accumulated charge, the final result is that the total charge of the first part of the pixels + the second part of the pixels (S11) - the charge of the first part of the pixels (S10) ≠ the charge of the second part of the pixels.

[0030] like Figure 5 As shown, the sampling process of pixel charge quantity using the related double sampling technique is as follows: Step 1: The photodiodes connecting the first and second part of the pixels accumulate charge simultaneously, and the amount of charge on both sides is the same; Step 2: Turn on the TG of the photodiode connected to the first part of the pixels, and first read the charge of the photodiode PD1 of the first part of the pixels; Step 3: Turn on the TG of the photodiode connected to the second part of the pixels and read out the accumulated charge of the photodiode PD2 of the second part of the pixels; since photoelectric accumulation also occurs during the TG period when reading the charge of the first part of the pixels, the photodiode will accumulate a small amount of charge when reading the charge of the second part of the pixels during this period. Step4: the pixel signals of the first part and the second part are read out, and in an ideal state, the pixel reading of the first part and the second part should be the same, but due to the small amount of charge accumulated in Step3, the final charge amount of the second part of the pixel is not equal to the charge amount of the first part of the pixel, which finally leads to a deviation of phase focusing.

[0031] The embodiment is to improve the accuracy of phase focusing, and aims to add the excess charge amount of the second part of the pixel to the charge amount of the first part of the pixel in the same proportion by means of digital-to-analog conversion, so that the charge amounts of the two parts of the same pixel remain the same level.

[0032] In some embodiments, the feedback coefficient generated in the exposure multiplication area is specifically: determining the exposure time and interval time required for reading the first part of the pixel charge amount and the second part of the pixel charge amount of the exposure multiplication area; calculating the proportional coefficient of phase focusing according to the exposure time and interval time; multiplying the proportional coefficient according to the preset conversion coefficient, the analog signal amount and the digital signal amount to obtain the feedback coefficient; wherein the conversion coefficient refers to the bias in the process of analog-to-digital conversion or digital-to-analog conversion.

[0033] As shown in Figure 1 , the exposure processing unit carried in the firmware S05 (Firmware) is used to calculate the proportional coefficient for compensating and adjusting the first part of the pixel. Since the exposure time is detected, the process of measuring and calculating the signal amount deviation between the first part of the pixel and the second part of the pixel can be programmed. In view of saving circuit area and simplifying the processing process, the firmware S05 is introduced. The function of the firmware S05 is to control the hardware. The exposure time processing unit is assembled in the firmware S05 to realize the control interaction with the image sensor.

[0034] The exposure processing unit specifically operates as follows: for the CDS reading schematic diagram of phase focusing pixels, as shown in Figure 6 , the Vrst part is the first reading reset noise (reset noise) value, the Vsig1 part is the charge amount of the first part of the pixel, the Vsig2 part is the total charge amount of the first part of the pixel plus the second part of the pixel, and the results of Vsig1-Vrst and Vsig2-Vrst are respectively the CDS results of the first part of the pixel and the CDS results of the first part of the pixel plus the second part of the pixel.

[0035] From the order of reading the exposure time, Vsig1 is first read out, and then Vsig2 is read out, and there is a certain time difference in the TG opening time. It is just because of the difference in this part of the exposure time that after CDS, the total charge amount of the first part of the pixels plus the second part of the pixels (S11) - the charge amount of the first part of the pixels (S10) ≠ the charge amount of the second part of the pixels. Therefore, the interval time ΔT, or the interval time difference ΔT, can be obtained, which is usually delayed in units of time; the exposure time T of reading the charge amount of the first part of the pixels plus the charge amount of the second part of the pixels can also be obtained, that is, the reading time of the first part of the pixels can be obtained through (T-ΔT). And according to the accumulation deviation of the charge amount in the reading process described above, therefore, the first part of the pixel Vsig1 needs to be compensated and adjusted (amplified) in this embodiment, in other words, the amplification ratio required for completing phase focusing is T / (T-ΔT). The ratio can also be referred to as the exposure time coefficient in the description below, and the coefficient is calculated by the exposure time processing unit of the phase detection focusing imaging system.

[0036] After determining the ratio coefficient for compensating and adjusting the first part of the pixel Vsig1, the digital signal processing unit S13 of the phase detection focusing imaging system performs multiplication processing, and the output obtained is fed back to the analog signal conversion (ADC) as a loop of the feedback system. The specific implementation process is as follows: When the ratio coefficient is 1, it can be known that the charge amounts of the first part of the pixels and the second part of the pixels remain at the same level, such as Figure 2 The phase difference of the focusing state shown in S08 in the middle is 0, which achieves the purpose of phase focusing.

[0037] Since the conversion target signals in the analog signal conversion (ADC) and the digital signal conversion (DAC) are consistent, and the processes are different, in an ideal state, ADC×DAC=conversion coefficient. It needs to be understood that the conversion coefficient is 1 in an ideal state, and in practice, the bias caused by gain or voltage or device factors in the ADC or DAC process can be controlled, so the conversion coefficient is used for unified description.

[0038] Thus, a closed-loop transfer function feedback system in an ideal state (conversion coefficient is 1) is constructed. The feedback channel of the feedback system S04 is 1, the forward path is analog pixel reading, and after reading by the analog signal conversion (ADC), it is transmitted to the digital circuit, and the ratio coefficient is obtained through the exposure processing unit. Then, the reverse path is constructed by the digital circuit, and the feedback coefficient S14 and the digital signal conversion (DAC) are returned to the relevant double sampling of the analog signal conversion (ADC) for processing.

[0039] The feedback coefficient of the first part of the pixels can be obtained as follows: a As follows: ; ; wherein, a represents a feedback coefficient, DAC represents an analog signal quantity processed by a digital-to-analog converter, ADC represents a digital signal quantity processed by an analog-to-digital converter, and T represents an exposure time, represents an interval time It should be noted that DAC / ADC appearing in the formula is determined by the bit width thereof, where ADC is a digital signal quantity processed by an analog-to-digital converter, and DAC is an analog signal quantity processed by a digital-to-analog converter.

[0040] For (T / (T-△T)) contained in the feedback coefficient, the problem that the charge quantity of the first part of pixels in the phase focus pixel is small due to the difference in exposure time is corrected, so as to increase the charge quantity of the first part of pixels, and finally achieve the expected effect that the total charge quantity of the first part of pixels and the second part of pixels minus the charge quantity of the first part of pixels is equal to the charge quantity of the second part of pixels.

[0041] Secondly, for the feedback system S04, it is specifically implemented as shown in Figure 7 : the first part of pixels is exposed, and after photoelectric conversion is completed, the proportion coefficient is obtained in an ADC (analog signal conversion) S12 in an exposure quantity processing unit, and digital signal processing is performed in a digital signal processing unit S13 after analog-to-digital conversion; a feedback path is constructed by a digital circuit, and after passing through a feedback coefficient S14 and a DAC (digital signal conversion) S15, the ADC (analog signal conversion) S12 is fed back to complete voltage biasing for analog-to-digital conversion, so as to achieve the purpose of amplifying the charge quantity of the first part of pixels.

[0042] It should be noted that in the process of converting the analog signal into a digital signal by the ADC (analog signal conversion) S12, loading the feedback coefficient S14 back to the analog signal for control, there is a certain time and space process to respond. In order to realize this part of response time, as shown in Figure 8 : the imaging area of the image sensor is divided into an exposure multiplication area S16 and an exposure processing area S17. Figure 8 Each block in

[0043] The exposure multiplication area S16 does not participate in phase focus adjustment and imaging but normally receives light, and the physical row number is usually 2 rows / 4 rows; the exposure processing area S17 normally receives light and participates in actual phase focus adjustment and imaging.

[0044] Therefore, the embodiment completes the calculation of the proportional coefficient and the digital signal processing in the exposure multiplication area S16, generates the feedback coefficient, and then performs digital-to-analog conversion on the feedback coefficient to obtain an analog signal. The value of the analog signal is used to raise the starting position of the slope voltage of the analog converter for reading the first-pixel charge amount, so as to increase the counting time for reading the first-pixel charge amount, complete the compensation of the first-pixel charge amount, and then timely take effect before reaching the exposure processing area S17, so as to achieve the compensation and adjustment of the target pixel (the first-pixel) in the same imaging area.

[0045] To prove the difference between the phase detection focusing method provided by the present application and the phase detection focusing method provided by the prior art, the following comparative example is further provided. As shown in Figure 9 , the ADC reading schematic diagram of the phase focusing pixel in the normal state is shown. The intersection point of each slope voltage and the Vin voltage is the quantization value of this stage, that is, the charge amount.

[0046] Based on Figure 9 , it can be obtained that the quantization value of Vrst in Figure 9 is 1; The quantization value of Vsig1 after CDS is 1; The quantization value of Vsig2 after CDS is 4; According to the readout sequence of the exposure time, the quantization value of Vsig1 is read out first, and Vsig2 is read out during which a part of interval time ΔT is additionally added based on the exposure time of Vsig1. The quantization value of the second-pixel caused by this part of interval time ΔT is (quantization value of the first-pixel + quantization value of the second-pixel) - quantization value of the first-pixel = 4 - 1 = 3. It can be seen that the quantization value of the first-pixel and the quantization value of the second-pixel are not equal.

[0047] Through the compensation process described above, the analog signal converted by the feedback coefficient is applied to Vsig1 to play a bias voltage role, as shown in Figure 10 , because when the exposure time difference is not compensated, the quantization value of Vsig2 after CDS is 4; Because the first-pixel value and the second-pixel value are expected to be equal before the phase focusing detection, it is obtained that the quantization value of the first-pixel and the quantization value of the second-pixel in Vsig2 are each 2; And the quantization value of the second part of pixels is (quantization value of the first part of pixels + quantization value of the second part of pixels) - quantization value of the first part of pixels = Vsig2 - Vsig1, Vsig1 is smaller than the expected value without exposure time compensation, so the feedback analog signal should increase the quantization value of Vsig1; According to Figure 10 It can be seen that the quantization value is the intersection of the ramp voltage and Vin, the longer the time required for the intersection, the larger the part of the pixel value, and the Vin voltage is determined by the original pixel and cannot be adjusted, so relatively speaking, when Vin is unchanged, the starting position of the ramp voltage of Vsig1 is lifted by a part to increase the count time of reading the first part of the pixel charge, that is, the purpose of compensating the Vsig1 signal is achieved, and the compensation ratio is (T / (T-△T); Therefore, Vrst is Figure 10 The quantization value in the first part of pixels is 1; The quantization value of Vsig1 after CDS offset voltage is 2; The quantization value of Vsig2 after CDS is 4; The quantization value of the second part of pixels is (quantization value of the first part of pixels + quantization value of the second part of pixels) - quantization value of the first part of pixels = Vsig2 - Vsig1 = 2, and the quantization values of the first part and the second part of pixels are equal after adjustment, so the focusing method provided by the embodiment can achieve phase focusing, and the image sensor outputs the pixel units in the exposure processing area as actual imaging pixels.

[0048] In summary of the above description, the exposure compensation provided by the embodiment itself improves the shutter speed and sensitivity, changes from the digital way to the analog way, completes the exposure compensation under the premise of ensuring the phase focusing characteristics, reduces the noise interference caused by the exposure time difference in the focusing circuit, and improves the focusing accuracy. At the same time, in order to ensure that the charge amount of each part of pixels before phase focusing is the same, the prior art usually increases the corresponding addition and multiplication digital processing circuit in the digital circuit to solve the signal amount deviation problem. The present application directly returns to the analog pixel structure through a feedback way, only adds a feedback path of a proportional coefficient, so that the charge amount of each part of pixels after CDS processing of the digital-analog converter is the same, and the charge amount compensation is ensured, thereby saving the digital circuit area and power consumption of the prior art.

[0049] The embodiment of the present application also provides a graphic sensor using a correlated double sampling technology, which is used for the phase detection focusing method described in the above embodiment.

[0050] Specifically, as Figure 1As shown, the pattern sensor adopting the correlated double sampling technology comprises a pixel array S01, an analog circuit S02, a digital circuit S03, a feedback system S04, firmware S05 and an application processor S06, more specifically, the feedback system S05 is composed of an analog signal conversion, a digital signal processing unit and a digital signal conversion, the analog circuit S02 is composed of a photoelectric conversion and an analog signal conversion, since each component has been clearly described in the foregoing embodiment description, no detailed description is made here.

[0051] The image sensor adopting the correlated double sampling technology provided by the embodiment generates a feedback coefficient for compensating the first part of pixels in the exposure processing region in the exposure multiplication region of the imaging region of the image sensor, and adjusts the reading voltage of the analog-digital conversion circuit based on the feedback coefficient, so as to realize the exposure compensation of the first part of pixels in the exposure processing region, so that there is no deviation between the first part of pixel charge and the second part of pixel charge read out by the exposure processing region, and the purpose of phase detection automatic focusing is achieved, and the focusing accuracy of the imaging process is improved.

[0052] The embodiment of the present application further provides a phase detection focusing imaging system, which comprises the pattern sensor adopting the correlated double sampling technology and an application processor.

[0053] Specifically, the phase detection focusing imaging system generates a feedback coefficient for compensating the first part of pixels in the exposure processing region in the exposure multiplication region of the imaging region of the image sensor, and adjusts the reading voltage of the analog-digital conversion circuit based on the feedback coefficient, so as to realize the exposure compensation of the first part of pixels in the exposure processing region, so that there is no deviation between the first part of pixel charge and the second part of pixel charge read out by the exposure processing region, and the purpose of phase detection automatic focusing is achieved, and the focusing accuracy of the imaging process is improved.

[0054] The embodiment of the present application further provides a terminal comprising the phase detection focusing imaging system.

[0055] Specifically, the terminal can take photos with high imaging quality, has the function of automatic focusing, and has high focusing accuracy, and the terminal can include but is not limited to a smart phone, a camera, a monitoring camera and the like.

[0056] The above detailed description of the specific embodiments of the present application has been given to understand the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A phase detection focusing method, applied to an image sensor employing correlation double sampling technology, characterized in that, The methods include: Based on the feedback coefficient generated in the exposure multiplication area, the analog-to-digital conversion process of the first part of the pixel charge in the exposure processing area is adjusted so that the first part of the pixel charge read from the exposure processing area is equal to the second part of the pixel charge, thus completing phase focusing.

2. The phase detection focusing method according to claim 1, characterized in that, The feedback coefficient generated in the exposure multiplication region is specifically as follows: Determine the exposure time and interval time required to read the pixel charge of the first part and the pixel charge of the exposure multiplication area; The phase-detection autofocus ratio coefficient is calculated based on the exposure time and interval time. The proportional coefficient is multiplied by the preset conversion coefficient, analog signal quantity, and digital signal quantity to obtain the feedback coefficient; wherein, the conversion coefficient refers to the bias in the analog-to-digital conversion or digital-to-analog conversion process.

3. The phase detection focusing method according to claim 2, characterized in that, The interval time is the time difference between two openings of the transmission gate of the photodiode connecting the first part of the pixels.

4. The phase detection focusing method according to claim 2, characterized in that, The phase-detection autofocus scaling factor is calculated based on the exposure time and interval time, specifically as follows: The reading time for reading the first part of the pixel charge is obtained based on the difference between the exposure time and the interval time. The ratio of exposure time to readout time is used to obtain the phase-detection autofocus scaling factor.

5. The phase detection focusing method according to claim 2, characterized in that, The conversion factor is 1.

6. The phase detection focusing method according to claim 2, characterized in that, The expression for multiplying the proportional coefficient based on the preset conversion factor, analog signal quantity, and digital signal quantity is as follows: ;in, a The input signal represents the feedback coefficient, the output signal represents the analog signal processed by the digital-to-analog converter (DAC), the output signal represents the digital signal processed by the analog-to-digital converter (ADC), and the output signal represents the exposure time. Indicates the interval time.

7. The phase detection focusing method according to claim 1, characterized in that, The analog-to-digital conversion process for the first portion of pixel charge in the exposure processing area is adjusted as follows: The feedback coefficients are converted from digital to analog to obtain an analog signal; The starting position of the ramp voltage of the analog converter used to read the first part of the pixel charge is raised according to the value of the analog signal, so as to increase the counting time for reading the first part of the pixel charge and complete the compensation of the first part of the pixel charge.

8. A pattern sensor employing correlated double sampling technology, characterized in that, Used to perform a phase detection focusing method as described in any one of claims 1 to 7.

9. A phase detection focusing imaging system, characterized in that, The phase detection focusing imaging system includes: A graphics sensor employing correlated double sampling technology as described in claim 8; and An application processor is used to process the pixel data output by the image sensor employing correlated double sampling technology to generate an image.

10. A terminal, characterized in that, Including a phase detection focusing imaging system as described in claim 9.

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