A filter wheel control method for multispectral arbitrary spectral band imaging

Abstract

The application belongs to the technical field of multispectral imaging system, and discloses a filter wheel control method for multispectral arbitrary spectrum imaging. The method compares the actually detected current position with the previously calibrated position, obtains the shortest path planning, avoids the detected blind area during the movement, drives the filter wheel to rotate according to the corresponding control curve stroke mode, so that the required filter aligns the optical path for imaging. The application has simple system structure requirement and simple control method implementation, can effectively and quickly complete the control of any filter in the filter wheel within half a cycle, and realizes multispectral time-sharing resident imaging.

Description

Technical Field

[0001] This invention relates to the field of multispectral imaging system technology, and in particular to a filter wheel control method for imaging in any multispectral band. Background Technology

[0002] To achieve multispectral imaging in optical remote sensing cameras, a set of filters is used to pass light of specific spectral bands through the filters for imaging, while light of other spectral bands is blocked. Considering factors such as weight and size, thin-walled bearing-type filter mechanisms are commonly used in optical remote sensing cameras. Large-size thin-walled bearing-type filter mechanisms typically have six or more filters, fixed in a filter wheel mechanism, which time-division multiplex the optical path and work in conjunction with the detector for imaging. To ensure the quality of multispectral image information, the positioning and repeatability accuracy of the filters need to be controlled.

[0003] In practical applications, stepper motors are commonly used to drive the filter wheel, in conjunction with Hall effect switches to switch the filters. During the rotation process, a reset is required first, followed by sequential rotation of adjacent filters. The signal detected by the Hall effect switch each time the filter passes the light path indicates whether it is aligned with the optical path. This method is sufficient for applications where filters are rotated sequentially in the same direction with a large margin for alignment error. However, due to the inherent characteristics of the Hall effect switches, they cannot provide unique position information for each filter. This means that the positioning accuracy of the filters cannot be guaranteed, and the mechanism cannot perform random switching of arbitrary spectral bands without a reset.

[0004] To address the aforementioned issues, Hall effect angular displacement sensors can be used to identify the unique position of each filter. However, even with sensors providing unique position feedback, factors such as mechanical transmission errors, the motor's own step angle error within a single cycle (360°), signal loss or errors due to interference in signal transmission, and insufficient current or unstable voltage due to power variations causing some output pulses to not travel along the motor's stepping path, mean that theoretically, using the motor's own step angle to obtain the drive pulse corresponding to the rotation angle required for each filter's structural position cannot accurately achieve the driving and positioning of any filter within the mechanism. The difficulty of accurate positioning increases with the number of filters. To improve multispectral imaging efficiency, it is often necessary to complete the rotational positioning of any filter within a single cycle using the shortest path; therefore, rotational path planning within a single cycle is crucial. Furthermore, during operation, it is necessary to overcome the blind zone control problem caused by the sensor's inability to provide 360° full coverage feedback. Although the blind zone is usually located in areas other than the filter's light-transmitting aperture, in the case of real-time position information association during movement, the true position information cannot be obtained for motor drive control. Therefore, in order to rapidly rotate any filter within a single cycle and accurately position it, it is necessary to develop a control method to meet the practical engineering needs of integrating many filters (usually more than 6) on a single filter wheel and having blind spots. Summary of the Invention

[0005] The present invention aims to provide a filter wheel control method for multispectral arbitrary band imaging, which can realize the rapid rotation of the filter wheel of any filter within a single cycle and accurate positioning.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A filter wheel control method for multispectral arbitrary band imaging includes the following steps:

[0008] Step 1: Initial calibration of the filter wheel system configuration, including the center position and tolerance range of each filter, the relationship between the rotation direction of the filter wheel and the Hall effect angular displacement sensor and the direction of output signal change, the corresponding blind zone position, and the relationship between the rotation angle and the amount of output signal change;

[0009] Step 2: Receive data instructions, determine the rotation direction of the filter wheel in the path planning based on the deviation between the current position and the target position, and estimate the number of control cycle drive steps;

[0010] Step 3: Based on the control frequency, estimated control cycle, number of drive steps, change in the output signal of the Hall effect angular displacement sensor corresponding to a single pulse of the filter wheel, and the corresponding blind zone position of the filter wheel and the Hall effect angular displacement sensor, complete the filter wheel rotation control according to the corresponding acceleration, constant speed, and deceleration control curves.

[0011] Step 4: Determine whether the current position is within the tolerance range of the required spectral segment position. If it is, end the control. If not, perform single-step fine-tuning according to the deceleration segment control frequency until the current position is within the tolerance range of the required spectral segment position and end the control.

[0012] Furthermore, in step two, determining the rotation direction of the filter wheel in the path planning includes:

[0013] When M > 0 and M > N, then it is set to rotate in the positive direction;

[0014] When M > 0 and M < N, then it is set to rotate in the opposite direction;

[0015] When M < 0 and M > N, then it is set to rotate in the opposite direction;

[0016] When M < 0 and M < N, then it is set to rotate in the positive direction;

[0017] Where M = VV i , where V is the current detection position V and V is the desired spectral band position V. i The calculated current position offset; The center position feedback value within the effective range of the Hall effect angular displacement sensor is obtained by rotating the filter wheel and detecting the output signal of the Hall effect angular displacement sensor. V- is the signal value when the output signal of the Hall effect angular displacement sensor no longer changes. Continue rotating the filter wheel, and V+ is the signal value when the output signal of the Hall effect angular displacement sensor changes again with rotation.

[0018] Furthermore, in step two, estimating the number of control cycle drive steps includes:

[0019] Taking the absolute value of the current position offset M, we get ΔV = |Vi - V|;

[0020] Based on the change in output signal ΔV0 of the Hall effect angular displacement sensor corresponding to a single drive pulse of the filter wheel, the number of drive steps in the control cycle, Step, is estimated.

[0021] Furthermore, in step three, the control of the filter wheel rotation specifically includes:

[0022] If the number of driving steps in the control cycle Step-4 > 0, then according to the determined direction, the acceleration segment and the constant speed segment control will begin according to the control frequency in the received instruction. In the constant speed segment, the feedback signal of the Hall effect angular displacement sensor will be associated to perform closed-loop control. When the difference between the feedback signal and the required spectral segment position ΔV′≤2ΔV0 is detected, the deceleration segment will be entered. After completion, the process will proceed to step four.

[0023] If the number of driving steps in the control cycle Step-4 ≤ 0, then according to the determined direction, the acceleration and deceleration control will begin according to the control frequency in the received instruction, and the Hall effect angular displacement sensor feedback signal will be associated throughout the process. When the difference between the feedback signal and the required spectral segment position ΔV′ ≤ 2ΔV0 times is detected, the deceleration segment will be entered, and after completion, step four will be entered.

[0024] If entry into the blind zone is detected during movement, the associated feedback signal is automatically canceled until the real-time position signal V leaves the blind zone range (V). + V - Then correlate the feedback signal.

[0025] Furthermore, in step four, after the control is terminated, a phase-locked operation is performed, and the phase-locked operation lasts for 2 seconds.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. By using the technical solution of the present invention, rotation and positioning of any spectral band within a single cycle can be achieved, so as to ensure that rotation is performed in the shortest time and the filter is accurately aligned with the optical path for time-division dwell imaging during multi-spectral band switching, thereby improving the efficiency of the imaging system and the integrity of the light path of the required spectral band.

[0028] 2. By using the technical solution of the present invention, the positioning accuracy of the filter can be improved, the coverage area of ​​each filter on the light-transmitting aperture can be reduced, and more filters can be installed on the same size filter wheel to achieve applications of more spectra.

[0029] 3. The proposed blind zone monitoring and control strategy reduces the performance requirements of hardware integration, thereby solving the problem of being unable to control the entire rotation cycle due to the defects of the device itself, and the method is simple and effective. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a filter wheel control method for multispectral arbitrary band imaging according to the present invention.

[0031] Figure 2 This is a schematic diagram of the filter wheel structure for multispectral arbitrary band imaging applied in this invention;

[0032] Figure 3 This is a schematic diagram showing the matching of the filter position and optical path in a filter wheel structure.

[0033] Figure 4 This is a schematic diagram of the filter wheel rotation control curve;

[0034] In the figure, the reference numerals include: 1. Wheel; 2. Light transmission aperture; 3. Filter; 4. Hall effect angular displacement sensor; 5. Motor; 6. Blind spot position; 7. Housing; 8. Drive and data acquisition controller; 9. Command transmission and position information display terminal; 10. Calibration positioning hole. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0036] like Figure 2 As shown, the purpose of this invention is to align each filter 3 with the light-transmitting aperture 2 in the shortest possible time. The drive component for rotating the wheel 1 is a motor 5, which, combined with the position feedback from the Hall effect angular displacement sensor 4, is used according to... Figure 4 The control curve controls the filter 3 on the wheel 1 to... Figure 3 Within the range shown, and within the control cycle, blind spot position 6 is avoided. The motor drive circuit and data acquisition circuit are integrated in the drive and data acquisition controller 8. The command sending and position information display terminal 9, motor 5 and sensor 4 are all electrically connected to the drive and data acquisition controller 8.

[0037] like Figure 1 The method shown is a filter wheel control method for multispectral arbitrary band imaging, comprising:

[0038] (a) Position calibration of the filter wheel system:

[0039] (1) Align each filter 3 with the light transmission aperture 2 in sequence using the calibration positioning hole 10. Read and record the voltage value Vi corresponding to the position of each filter 3 through the command sending and position information display terminal 9. There are a total of 6 filters, but not limited to 6. Number the voltage value Vi corresponding to the position of each filter 3, and denote it as Bi.

[0040] (2) Receive the forward or reverse command of motor 5 respectively, and determine the direction of change of the feedback (output) signal of Hall angular displacement sensor 4. The result in the actual calibration process shall prevail. For the purpose of describing the following method steps, it is assumed that the position feedback signal of Hall angular displacement sensor 4 increases when rotating forward.

[0041] (3) Move each filter 3 to the position shown in the image. Figure 3 At the positions shown, the voltage values ​​corresponding to the positions of each filter 3 are read and recorded by the command sending and position information display terminal 9, thereby determining the upper and lower limits of the allowable positions of each filter 3, Vi+, Vi-, i∈1-6. According to the sensor characteristics, Vi+>Vi>Vi- here.

[0042] (4) Repeat steps (1) and (3) 3 times each, and calculate the average value to obtain the voltage value Vi corresponding to the center position of each filter 3 and the upper and lower limits of the allowed position of each filter 3, Vi+, Vi-.

[0043] (5) Rotate the wheel 1 in the forward direction until the feedback signal of the Hall angular displacement sensor 4 stops changing and mark the current position x1 and the feedback signal V- of the sensor 4 on the housing 7. Continue to rotate the wheel until the feedback signal of the Hall angular displacement sensor 4 starts to change and stop rotating. Mark the current position x2 and the feedback signal V+ of the sensor 4 on the housing 7 and measure the angle θ from x1 to x2 with a protractor.

[0044] (6) Rotate the wheel 1 in the opposite direction until the feedback signal of the Hall angular displacement sensor 4 stops changing and mark the current position x2 and the feedback signal V+ of the Hall angular displacement sensor 4 on the outer casing 7. Then continue to rotate the wheel 1 until the feedback signal of the Hall angular displacement sensor 4 starts to change and stop rotating. Mark the current position x1 and the feedback signal V- of the Hall angular displacement sensor 4 on the outer casing 7 and measure the angle θ from x2 to x1 with a protractor.

[0045] (7) Repeat steps (5) and (6) 3 times each, and calculate the average value to obtain the blind zone position V+, V- and rotation angle θ.

[0046] (8) Based on step (7), the center position feedback value within the effective range of Hall effect angular displacement sensor 4 is finally obtained. The change in the output signal of Hall effect angular displacement sensor 4 corresponding to each drive pulse (each step) Where θ0 is the step angle, an inherent property of motor 5.

[0047] (9) Store the calibration results obtained in steps (4), (7) and (8) in the driver and data acquisition controller 8.

[0048] (II) Shortest path planning for arbitrary spectral segment rotation of the filter wheel:

[0049] (1) Receive data commands, which include the target spectrum number Bi and the control frequency f. -1 f -2 f, f +1 f +2 wait.

[0050] (2) Based on the spectral segment number in the received instruction, deduce the corresponding voltage value Vi, collect the voltage value V at the current position, and calculate the current position offset M = VV. i .

[0051] (3) The drive and data acquisition controller 8 determines the rotation direction of the motor 5 based on the calculated current position offset:

[0052] When M > 0 and M > N, then it is set to rotate in the positive direction;

[0053] When M > 0 and M < N, then it is set to rotate in the opposite direction;

[0054] When M < 0 and M > N, then it is set to rotate in the opposite direction;

[0055] When M < 0 and M < N, then it is set to rotate in the positive direction;

[0056] Where N is the feedback value of the center position point within the effective range of Hall effect angular displacement sensor 4.

[0057] (4) Take the absolute value of the current position offset M to obtain ΔV=|Vi-V|.

[0058] (5) Estimate the number of control cycle driving steps Step based on step (4), i.e. Where ΔV0 is the change in the output signal of the Hall effect angular displacement sensor 4 corresponding to each drive pulse in the drive and data acquisition controller 8.

[0059] (III) Rotation control of the filter wheel:

[0060] (1) Development of filter wheel rotation control curve:

[0061] ① Set two steps as acceleration segments in the initial segment, with driving frequencies of f and f respectively. -1 f -2 ;

[0062] ② Set the middle section as a constant speed section with a driving frequency of f;

[0063] ③ Two deceleration stages are set at the tail section, with driving frequencies f and f respectively. +1 f +2 .

[0064] (2) Make corresponding judgments on the estimated control cycle driving step number Step:

[0065] ①If Step-4 > 0, then proceed to step (3);

[0066] ②If Step-4≤0, then proceed to step (4).

[0067] During this stage, the number of steps in the acceleration phase can be adjusted according to different loads. If the acceleration phase is n steps, it is only necessary to satisfy n < step. Step-4 in step (2) is then represented as Step-(n+2).

[0068] (3) According to the rotation direction determined in (II), start the acceleration segment and the constant speed segment control according to the control frequency in the received instruction. In the constant speed segment, use the feedback signal of Hall angular displacement sensor 4 to perform closed-loop control. When the difference between the feedback signal and the required spectrum segment position ΔV′≤2ΔV0 is detected, enter the deceleration segment. After completion, proceed to step (5).

[0069] (4) Cancel the uniform speed section. According to the rotation direction determined in (II), start the acceleration and deceleration control according to the control frequency in the received instruction, and perform the entire process in conjunction with the feedback signal. When the difference between the feedback signal and the required spectrum position ΔV′≤2ΔV0 times is detected, enter the deceleration section. After completion, proceed to step (5).

[0070] (5) Determine whether the current position is within the tolerance range of the required spectrum segment position Vi+-Vi-. If it is satisfied, end the control. If it is not satisfied, perform single-step fine adjustment according to the deceleration segment frequency until the tolerance range position Vi+-Vi- is satisfied and end the control.

[0071] (6) If entering the blind zone is detected during the movement, the associated feedback signal is automatically canceled until the real-time position signal V leaves the blind zone range (V+, V-) and the associated feedback signal is re-associated, and the control is continued according to steps (3) and (4);

[0072] (7) After the rotation stops, a phase-locking operation is performed, and the phase-locking operation lasts for 2 seconds.

[0073] The above descriptions are merely embodiments of the present invention, and common technical solutions and / or characteristics known in the solutions are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A filter wheel control method for multispectral arbitrary band imaging, characterized in that, Includes the following steps: Step 1: Initial calibration of the filter wheel system configuration, including the center position and tolerance range of each filter, the relationship between the rotation direction of the filter wheel and the Hall effect angular displacement sensor and the direction of output signal change, the corresponding blind zone position, and the relationship between the rotation angle and the amount of output signal change; Step 2: Receive data instructions, determine the rotation direction of the filter wheel in the path planning based on the deviation between the current position and the target position, and estimate the number of control cycle drive steps; Step 3: Based on the control frequency, estimated control cycle, number of drive steps, change in the output signal of the Hall effect angular displacement sensor corresponding to a single pulse of the filter wheel, and the corresponding blind zone position of the filter wheel and the Hall effect angular displacement sensor, complete the filter wheel rotation control according to the corresponding acceleration, constant speed, and deceleration control curves. Step 4: Determine whether the current position is within the tolerance range of the required spectral segment position. If it is, end the control. If not, perform single-step fine-tuning according to the deceleration section control frequency until the current position is within the tolerance range of the required spectral segment position and end the control. In step two, determining the rotation direction of the filter wheel in the path planning includes: When M > 0 and M > N, then it is set to rotate in the positive direction; When M > 0 and M < N, then it is set to rotate in the opposite direction; When M < 0 and M > N, then it is set to rotate in the opposite direction; When M < 0 and M < N, then it is set to rotate in the positive direction; in, , is the current detection location and the position of the required spectral band The calculated current position offset; The signal is the center position feedback value within the effective range of the Hall effect angular displacement sensor. The filter wheel is rotated to detect the output signal of the Hall effect angular displacement sensor. To obtain the signal value at which the Hall effect angular displacement sensor output signal no longer changes, continue rotating the filter wheel. The signal value of the Hall effect angular displacement sensor output signal changes again with rotation.

2. The filter wheel control method for multispectral arbitrary band imaging according to claim 1, characterized in that, In step two, estimating the number of control cycle drive steps includes: Taking the absolute value of the current position offset M yields =| - |; Based on the change in the output signal of the Hall effect angular displacement sensor corresponding to a single drive pulse of the filter wheel The estimated control cycle number of steps is Step, i.e., Step = .

3. The filter wheel control method for multispectral arbitrary band imaging according to claim 2, characterized in that, Step three, specifically the control of the filter wheel rotation, includes: If the control cycle drive step number Step-4 > 0, then according to the determined direction, the acceleration and constant speed control will begin according to the control frequency in the received command. In the constant speed segment, closed-loop control will be performed by associating the feedback signal from the Hall effect angular displacement sensor. When the difference between the feedback signal and the desired spectral segment position is detected... ≤2 Enter the deceleration phase; after completion, proceed to step four. If the control cycle drive step number Step-4≤0, then according to the determined direction, the acceleration and deceleration control will begin according to the control frequency in the received command, and the Hall effect angular displacement sensor feedback signal will be continuously monitored. When the difference between the feedback signal and the required spectral segment position is detected... ≤2 After the deceleration phase is completed, proceed to step four. If a blind zone is detected during movement, the associated feedback signal is automatically canceled until the real-time position signal is received. Leave the blind spot area ( , Then correlate the feedback signal.

4. The filter wheel control method for multispectral arbitrary band imaging according to claim 3, characterized in that: In step four, after the control is terminated, a phase-locked operation is performed, and the phase-locked operation lasts for 2 seconds.

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