Calibration Device and Method for Imaging Uniformity of an Ultra-Large Area Array Infrared Image Sensor

Abstract

The present invention discloses a calibration device and method for the imaging uniformity of an ultra-large area array infrared image sensor, belonging to the field of infrared image sensor imaging. The present invention optimizes the transmission direction of the Gpol signal to compensate for the floating ground effect of the ground level. Through the reverse transmission of the two, the goal that the change trends of the Gpol signal and the ground level voltage are consistent is achieved; on the other hand, through the difference monitoring mechanism, the voltage difference between the Gpol signal and the ground level is detected, and by configuring the number of cascaded ground leakage diodes of the Gpol signal, the voltage drop degree of the Gpol signal from the middle to both sides is adjusted to achieve the goal that the change trends of the Gpol signal and the ground level voltage are the same and the amplitudes are consistent, ensuring that the voltage difference between the Gpol signal and the ground level is constant and realizing high-uniformity imaging. The present invention effectively solves the problem that the voltage difference between the Gpol signal and the ground level is not constant caused by the large area floating ground effect of the traditional image sensor.

Description

Technical Field

[0001] The present invention belongs to the field of infrared image sensor imaging, and in particular to a calibration device and method for imaging uniformity of an ultra-large area array infrared image sensor. Background Technique

[0002] The ultra-large area array infrared image sensor has the characteristics of large field of view and high resolution, and is widely used in typical application fields such as high-resolution earth observation, target detection and recognition. Due to the large scale of the area array of the ultra-large area array infrared image sensor, the data and ground signal transmission links are long, and the floating ground effect generated will cause differences in the bias voltage of the photosensitive diodes and differences in the on-resistance of the transmission transistors, resulting in inconsistent generation and transfer efficiency of photo charges, leading to the problem of poor imaging uniformity.

[0003] The traditional single photodiode pixel and pixel-level circuit are as Figure 1 shown, including ground signal 10, photodiode 11, transmission transistor 12, etc. Among them, Figure 1 the part other than the photodiode 11 is collectively referred to as the pixel-level circuit. The photodiode 11 collects the photoelectric signal, transfers and stores the photoelectric signal through the transmission transistor 12, and the subsequent stage completes tasks such as sampling, amplification and conversion. The longitudinal structure of the infrared image sensor is as Figure 2 shown, an infrared focal plane 33-1 is composed of an array of multiple photodiodes 11, a focal plane readout circuit 33-2 is composed of an array of multiple pixel-level circuits, and the ground drive 32 provides a ground level input for the focal plane readout circuit 33-2. The infrared focal plane 33-1 and the focal plane readout circuit 33-2 are interconnected by indium pillars. The overall structure of the infrared image sensor after being interconnected by indium pillars is as Figure 3 shown, including a plane array drive circuit 31, a ground drive 32, an infrared focal plane and readout circuit 33, an SPI interface circuit and control logic 35, a column readout circuit 36, and a ground transmission line 37. The plane array drive circuit 31 provides the control and drive timing of the pixel-level circuit for the entire plane array. The ground drive 32 provides a ground level and a ground drive for the infrared focal plane 33-1. Since the ground plane source of the infrared focal plane 33-1 is only the ground drive 32, the position of the infrared focal plane 33-1 close to the ground drive 32 is closer to the ground level. However, due to the large scale of the plane array, the floating ground effect will occur at the position far from the ground drive 32, resulting in a voltage increase.

[0004] Figure 4 shown is the ground level transmission method of the infrared image sensor after being interconnected by indium pillars. The ground drive 32 is the source of the ground level of the infrared focal plane, and the ground level is transmitted from both sides to the middle. Therefore, the floating ground effect is most obvious and the voltage is the highest at the middle position of the plane array. As Figure 5 shown, as the ground level Ground is transmitted from left to right, the ground level gradually rises from 0V to 0.3V. This ground level corresponds to a single pixel asFigure 1 Mid - ground signal 10. If no calibration measures are taken, for the gate control signal Gpol of the transmission transistor 12, due to the small gate - drain electrode, the voltage drop caused by the change of Gpol with distance is not obvious. Therefore, the voltage difference between Gpol at different physical positions and the ground level Ground is a variable value, and there are significant differences between Δ1 and Δ2, resulting in inconsistent generation and transfer efficiency of optical charges and causing the problem of poor imaging uniformity. Summary of the Invention

[0005] The object of the present invention is to overcome the above - mentioned disadvantages of the prior art and provide a calibration device and method for the imaging uniformity of a super - large - area array infrared image sensor.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A calibration device for the imaging uniformity of a super - large - area array infrared image sensor, including an infrared image sensor, and a floating - ground - effect compensation photodiode array is connected to the infrared image sensor;

[0008] During imaging, the ground - driven ground level Ground in the infrared image sensor is transmitted from both sides of the infrared focal plane and the read - out circuit to the middle; at the same time, the gate control signal Gpol of the transmission transistor transmitted to the middle of the infrared focal plane and the read - out circuit is transmitted from the middle to both sides. During the transmission from the middle to both sides, the gate control signal Gpol of the transmission transistor passes through the gate stage of the transmission transistor and the floating - ground - effect compensation photodiode array column by column;

[0009] Through the reverse transmission of the gate control signal Gpol and the ground level Ground, the goal of consistent change trends of the Gpol signal and the ground - level voltage is achieved.

[0010] Further, it also includes a difference monitoring array and an automatic comparison configuration unit;

[0011] During imaging, the difference monitoring array is used to monitor the amplitude of the floating - ground voltage generated when transmitted from both sides of the infrared focal plane and the read - out circuit to the middle;

[0012] The automatic comparison configuration unit is used to configure the photodiodes in the floating - ground - effect compensation photodiode array based on the amplitude of the floating - ground voltage to achieve the calibration of the floating - ground - effect compensation.

[0013] Further, the difference monitoring array is used to collect the first Gpol signal on one side of the infrared focal plane and the readout circuit, the ground level Ground, the intermediate Gpol signal of the infrared focal plane and the readout circuit, the second Gpol signal on the other side of the infrared focal plane and the readout circuit, and the ground level Ground, and obtain the first difference between the first Gpol signal and the ground level Ground, the second difference between the intermediate Gpol signal and the ground level Ground on this side, the third difference between the intermediate Gpol signal and the ground level Ground on the other side, and the fourth difference between the second Gpol signal and the ground level Ground on the other side;

[0014] The automatic comparison configuration unit is used to compare the differences. If the difference between the first difference and the second difference is less than a preset value, and the difference between the fourth difference and the third difference is less than a preset value, it is determined that the change amplitudes of the Gpol signal and the ground level are consistent;

[0015] Otherwise, it is determined that the change amplitudes of the Gpol signal and the ground level are inconsistent, and the floating ground effect compensation is performed by adjusting the number of photodiodes connected to the photodiode array.

[0016] Further, the automatic comparison configuration unit is used to compare the amplitudes of the first difference and the second difference. If the first difference is greater than the second difference, the number of photodiodes connected to the floating ground effect compensation photodiode array is increased to increase the leakage current and thus increase the voltage drop.

[0017] Further, the automatic comparison configuration unit is used to compare the amplitude differences of the first difference and the second difference corresponding to different configured photodiodes, and the diode configuration with the smallest amplitude difference is used as the final configuration.

[0018] A calibration method for the imaging uniformity of a large-area array infrared image sensor:

[0019] During imaging, the ground level Ground driven by the ground in the infrared image sensor is transmitted from both sides of the infrared focal plane and the readout circuit to the middle;

[0020] At the same time, the gate control signal Gpol of the transmission transistor transmitted to the middle of the infrared focal plane and the readout circuit is transmitted from the middle to both sides. During the transmission from the middle to both sides, the gate control signal Gpol of the transmission transistor passes through the gate stage of the transmission transistor and the floating ground effect compensation photodiode array column by column;

[0021] Through the reverse transmission of the gate control signal Gpol and the ground level Ground, the goal of making the voltage change trends of the Gpol signal and the ground level consistent is achieved.

[0022] Further, during the imaging process, monitor the magnitude of the floating ground voltage generated when transmitting from both sides of the infrared focal plane and the readout circuit towards the middle;

[0023] Configure the photodiodes in the floating ground effect compensation photodiode array based on the magnitude of the floating ground voltage, and realize the calibration of the floating ground effect compensation.

[0024] Further, collect the first Gpol signal, the ground level Ground, the middle Gpol signal of the infrared focal plane and the readout circuit, the second Gpol signal on the other side of the infrared focal plane and the readout circuit, and the ground level Ground, and obtain the first difference between the first Gpol signal and the ground level Ground, the second difference between the middle Gpol signal and the ground level Ground on this side, the third difference between the middle Gpol signal and the ground level Ground on the other side, and the fourth difference between the second Gpol signal and the ground level Ground on the other side;

[0025] If the difference between the first difference and the second difference is less than a preset value, and the difference between the fourth difference and the third difference is less than the preset value, it is determined that the change amplitudes of the Gpol signal and the ground level are consistent;

[0026] Otherwise, it is determined that the change amplitudes of the Gpol signal and the ground level are inconsistent, and adjust the number of photodiodes connected to the photodiode array to perform floating ground effect compensation.

[0027] Further, when the change amplitudes of the Gpol signal and the ground level are inconsistent, compare the magnitudes of the first difference and the second difference. If the first difference is greater than the second difference, increase the number of photodiodes in the floating ground effect compensation photodiode array to increase the leakage current and thus increase the voltage drop.

[0028] Further, when different numbers of diodes are connected to the floating ground effect compensation photodiode array, compare the magnitude differences of the first difference and the second difference corresponding to different numbers of diodes, and configure the diode with the smallest magnitude difference as the final configuration.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] Calibration device and method for imaging uniformity of the ultra-large area array infrared image sensor of the present invention. The floating ground effect compensation optimizes the transmission direction of the Gpol signal to compensate for the floating ground effect of the ground level. Through the reverse transmission of the two, the goal that the change trends of the Gpol signal and the ground level voltage are consistent is achieved. On the other hand, through the difference monitoring mechanism, the voltage difference between the Gpol signal and the ground level is detected. By configuring the number of cascaded ground leakage diodes of the Gpol signal, the voltage drop degree of the Gpol signal from the middle to both sides is adjusted to achieve the goal that the change trends of the Gpol signal and the ground level voltage are the same and the amplitudes are consistent, ensuring that the voltage difference between the Gpol signal and the ground level is constant and realizing high-uniformity imaging. The present invention effectively solves the problem that the voltage difference between the Gpol signal and the ground level is not constant caused by the large area floating ground effect of the traditional image sensor. Through the reverse transmission of the Gpol signal and the ground level, the consistency of the voltage change trends of the two is ensured; by connecting the compensation photodiode, the consistency of the voltage change amplitudes of the two is ensured, thus ensuring the high-uniformity imaging requirements. Description of the Drawings

[0031] Figure 1 is the pixel and pixel-level circuit structure;

[0032] Figure 2 is the overall structure of the 3D stacked infrared image sensor;

[0033] Figure 3 is the structure of the existing infrared image sensor;

[0034] Figure 4 is the schematic diagram of the transmission directions of the existing ground level Ground and the gate signal Gpol;

[0035] Figure 5 is the difference diagram of the ground level Ground and the gate signal Gpol under the existing architecture;

[0036] Figure 6 is the overall architecture of the high-uniformity infrared image sensor;

[0037] Figure 7 is the specific structure of the floating ground effect automatic calibration type infrared image sensor;

[0038] Figure 8 is the difference diagram of the ground level Ground and the gate signal Gpol under the structure of the present invention.

[0039] Among them, 10 - ground signal; 11 - photodiode; 12 - transfer transistor; 31 - area array driving circuit; 32 - ground driving; 33 - infrared focal plane and readout circuit; 33-1 - infrared focal plane; 33-2 - focal plane readout circuit; 35 - SPI interface circuit and control logic; 36 - column readout circuit; 37 - ground transmission line; 38 - first Gpol signal transmission line; 39 - first Gpol signal supply line; 40 - second Gpol signal transmission line; 41 - second Gpol signal supply line; 42 - floating ground effect compensation photodiode array; 43 - difference monitoring array; 44 - automatic comparison configuration unit; 45 - first difference; 46 - second difference; 47 - fourth difference; 48 - third difference; 91 - first switch; 92 - second switch; 93 - third switch; 94 - fourth switch. Detailed implementation manners

[0040] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0041] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings:

[0043] The present invention proposes a constant pressure difference self-calibration and floating ground effect compensation method for high-uniformity imaging. The floating ground effect compensation optimizes the transmission direction of the Gpol signal to compensate for the floating ground effect of the ground level. Through the reverse transmission of the two, the goal of consistent change trends of the Gpol signal and the ground level voltage is achieved. The constant pressure difference self-calibration detects the voltage difference between the Gpol signal and the ground level through a difference monitoring mechanism, and adjusts the voltage drop degree of the Gpol signal from the middle to both sides by configuring the number of cascaded ground diodes of the Gpol signal. The more cascaded diodes, the greater the ground leakage, and the more obvious the voltage drop degree, so as to achieve the goal of the same change trend and the same amplitude between the Gpol signal and the ground level voltage, ensuring a constant pressure difference between the Gpol signal and the ground level.

[0044] The specific working process is as Figure 6 shown. The first Gpol signal transmission line 38 and the second Gpol signal transmission line 40 transmit the Gpol signal from both sides to the middle. During the transmission process, no devices are connected, so there is no leakage channel, and the level value of the Gpol signal is completely transmitted to the middle. Then, using the first Gpol signal supply line 39 and the second Gpol signal supply line 41, the Gpol signal is transmitted from the middle to both sides. During the transmission process, the gate stages of the transmission transistors 12 are connected column by column, and at the same time, the floating ground effect compensation photodiode array 42 is connected column by column. Therefore, when the Gpol is transmitted from the middle to both sides, due to the weak ground leakage of the compensation photodiodes in the floating ground effect compensation photodiode array 42, the voltage value of the Gpol signal decreases column by column, and the middle level of the Gpol signal is higher and the levels on both sides are lower. The voltage drop characteristic of the Gpol signal is consistent with the trend of the ground level being lower on both sides and higher in the middle. Through the reverse transmission of the Gpol signal and the ground signal, the consistent change trends of the two are achieved, and the compensation is realized.

[0045] To ensure the same pressure difference between the Gpol signal and the ground signal, not only the change trends of the Gpol signal and the ground signal need to be the same, but also the change amplitudes of the two need to be the same. As Figure 6 shown, a difference monitoring array 43 is used to collect the first difference 45 between the first Gpol signal on one side and the ground level, the second difference 46 and the third difference 48 between the middle Gpol signal and the ground levels on both sides, and the fourth difference 47 between the second Gpol signal on the other side and the ground level. If the values of the first difference 45 and the second difference 46 are close, and the values of the fourth difference 47 and the third difference 48 are close, then the change amplitudes of the Gpol signal and the ground level are the same, as Figure 8 shown. If the difference between the first difference 45 and the second difference 46 is large, and the difference between the fourth difference 47 and the third difference 48 is large, then the change amplitudes of the Gpol signal and the ground level are quite different, and automatic calibration is performed.

[0046] The specific implementation process of constant differential pressure self-calibration is as follows. Figure 7 , connect the floating ground effect compensation photodiode array 42, and close the first switch 91 and the second switch 92 to connect part of the compensation photodiodes. The automatic comparison configuration unit 44 compares the amplitudes of the first difference 45 and the second difference 46. If the first difference 45 is greater than the second difference 46, as Figure 8 , it indicates that the voltage drop of the first Gpol signal from the middle to the first transmission is too small, so the leakage is increased to achieve an increase in the voltage drop. Therefore, by closing the third switch 93 and the fourth switch 94 respectively, more photodiodes in the floating ground effect compensation photodiode array 42 are connected to increase the voltage drop for matching the floating ground effect. First, close the third switch 93, calculate the amplitude difference between the first difference 45 and the second difference 46, then close the third switch 93 and the fourth switch 94, and calculate the amplitude difference between the first difference 45 and the second difference 46. The switch configuration with the smallest amplitude difference is taken as the final configuration. Similarly, if the first difference 45 is less than the second difference 46, as Figure 8 , it indicates that the voltage drop of the first Gpol signal from the middle to the first transmission is too large, and the leakage needs to be reduced to achieve an increase in the voltage drop. Therefore, it is necessary to reduce the diodes in the floating ground effect compensation photodiode array 42 by disconnecting the first switch 91 and the second switch 92 respectively to reduce the voltage drop for matching the floating ground effect. First, disconnect the first switch 91, calculate the amplitude difference between the first difference 45 being less than the second difference 46, then disconnect the first switch 91 and the second switch 92, and calculate the amplitude difference between the first difference 45 and the second difference 46. The switch configuration with the smallest amplitude difference is taken as the final configuration. The same automatic configuration process is adopted for the other side to achieve automatic calibration. Through reverse transmission, trend-consistent calibration is achieved. Through the constant differential pressure self-calibration technology, variation amplitude matching calibration is achieved, and finally, the constant differential pressure between the Gpol signal and the ground level is achieved. The bias voltages of the photodiodes and the on-resistances of the transmission transistors are consistent among columns, and the generation and transfer efficiencies of the optical charges are consistent, achieving high uniformity imaging of the full array.

[0047] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A calibration device for the imaging uniformity of an ultra-large area array infrared image sensor, characterized in that It includes an infrared image sensor, and a floating ground effect compensation photodiode array (42) is connected to the infrared image sensor; During imaging, the ground level Ground of the ground drive (32) in the infrared image sensor is transmitted from both sides of the infrared focal plane and the readout circuit (33) to the middle; at the same time, the gate control signal Gpol of the transmission transistor (12) transmitted to the middle of the infrared focal plane and the readout circuit (33) is transmitted from the middle to both sides. During the transmission from the middle to both sides, the gate control signal Gpol of the transmission transistor (12) passes through the gate stage of the transmission transistor (12) and the floating ground effect compensation photodiode array (42) column by column; Through the reverse transmission of the gate control signal Gpol and the ground level Ground, the goal that the change trends of the Gpol signal and the ground level voltage are consistent is achieved.

2. The calibration device for the imaging uniformity of an ultra-large area array infrared image sensor according to claim 1, characterized in that, It further includes a difference monitoring array (43) and an automatic comparison configuration unit (44); During imaging, the difference monitoring array (43) is used to monitor the amplitude of the floating ground voltage generated when transmitting from both sides of the infrared focal plane and the readout circuit (33) to the middle; The automatic comparison configuration unit (44) is used to configure the photodiodes in the floating ground effect compensation photodiode array (42) based on the amplitude of the floating ground voltage to achieve the calibration of the floating ground effect compensation.

3. The calibration device for the imaging uniformity of a super-large area array infrared image sensor according to claim 2, wherein, The difference monitoring array (43) is used to collect the first Gpol signal on one side of the infrared focal plane and the readout circuit (33), the ground level Ground, the middle Gpol signal of the infrared focal plane and the readout circuit (33), the second Gpol signal on the other side of the infrared focal plane and the readout circuit (33), and the ground level Ground, and obtain the first difference (45) between the first Gpol signal and the ground level Ground, the second difference (46) between the middle Gpol signal and the ground level Ground on this side, the third difference (48) between the middle Gpol signal and the ground level Ground on the other side, and the fourth difference (47) between the second Gpol signal and the ground level Ground on the other side; The automatic comparison configuration unit (44) is used to compare the differences. If the difference between the first difference (45) and the second difference (46) is less than a preset value, and the difference between the fourth difference (47) and the third difference (48) is less than a preset value, it is determined that the change amplitudes of the Gpol signal and the ground level are consistent; Otherwise, it is determined that the change amplitudes of the Gpol signal and the ground level are inconsistent, and the floating ground effect compensation is performed by adjusting the number of photodiodes connected to the photodiode array (42).

4. A calibration device for the imaging uniformity of an ultra-large area array infrared image sensor according to claim 3, characterized in that, The automatic comparison configuration unit (44) is used to compare the amplitudes of the first difference (45) and the second difference (46). If the first difference (45) is greater than the second difference (46), the number of photodiodes connected to the floating ground effect compensation photodiode array (42) is increased to increase the leakage current and thus increase the voltage drop.

5. The calibration device for the imaging uniformity of an ultra-large area array infrared image sensor according to claim 4, characterized in that, The automatic comparison configuration unit (44) is used to compare the amplitude differences of the first difference (45) and the second difference (46) corresponding to different configured photodiodes, and use the diode configuration with the smallest amplitude difference as the final configuration.

6. A calibration method for the imaging uniformity of an ultra-large area array infrared image sensor, characterized in that: During imaging, the ground level Ground of the ground drive (32) in the infrared image sensor is transmitted from both sides of the infrared focal plane and the readout circuit (33) to the middle; At the same time, the gate control signal Gpol of the transmission transistor (12) transmitted to the middle of the infrared focal plane and the readout circuit (33) is transmitted from the middle to both sides. During the transmission from the middle to both sides, the gate control signal Gpol of the transmission transistor (12) passes through the gate stage of the transmission transistor (12) and the floating ground effect compensation photodiode array (42) column by column; Through the reverse transmission of the gate control signal Gpol and the ground level Ground, the goal that the change trends of the Gpol signal and the ground level voltage are consistent is achieved.

7. A calibration method for the imaging uniformity of an ultra-large area array infrared image sensor according to claim 6, characterized in that, During the imaging process, monitor the amplitude of the floating ground voltage generated when transmitting from both sides of the infrared focal plane and the readout circuit (33) to the middle; Configure the photodiodes in the floating ground effect compensation photodiode array (42) based on the amplitude of the floating ground voltage to achieve the calibration of the floating ground effect compensation.

8. A calibration method for the imaging uniformity of a super-large area array infrared image sensor according to claim 6, characterized in that The process of monitoring the amplitude of the floating ground voltage is as follows: Collect the first Gpol signal on one side of the infrared focal plane and the readout circuit (33), the ground level Ground, the middle Gpol signal of the infrared focal plane and the readout circuit (33), the second Gpol signal on the other side of the infrared focal plane and the readout circuit (33), and the ground level Ground, and obtain the first difference (45) between the first Gpol signal and the ground level Ground, the second difference (46) between the middle Gpol signal and the ground level Ground on this side, the third difference (48) between the middle Gpol signal and the ground level Ground on the other side, and the fourth difference (47) between the second Gpol signal and the ground level Ground on the other side; If the difference between the first difference (45) and the second difference (46) is less than a preset value, and the difference between the fourth difference (47) and the third difference (48) is less than a preset value, it is determined that the change amplitudes of the Gpol signal and the ground level are consistent; Otherwise, it is determined that the change amplitudes of the Gpol signal and the ground level are inconsistent, and the number of photodiodes connected to the photodiode array (42) is adjusted to perform floating ground effect compensation.

9. The calibration method for the imaging uniformity of an ultra-large area array infrared image sensor according to claim 8, characterized in that, When the change amplitudes of the Gpol signal and the ground level are inconsistent, compare the amplitudes of the first difference (45) and the second difference (46). If the first difference (45) is greater than the second difference (46), increase the number of photodiodes in the floating ground effect compensation photodiode array (42) to increase the leakage current and thus increase the voltage drop.

10. A calibration method for the imaging uniformity of an ultra-large area array infrared image sensor according to claim 9, characterized in that, When different numbers of diodes are connected to the floating ground effect compensation photodiode array (42), compare the amplitude differences of the first difference (45) and the second difference (46) corresponding to different numbers of diodes, and configure the diode with the smallest amplitude difference as the final configuration.

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