Space curve trigger signal generation system based on TDI line scanning camera

Abstract

The invention discloses a space curve trigger signal generation system based on a TDI line scanning camera, relates to the technical field of signal generation, and creatively provides the space curve trigger signal generation system based on the TDI line scanning camera based on a period detection unit and an interpolation compensation unit. The problem that an existing TDI line scanning camera cannot generate a line trigger signal during space three-dimensional curve scanning is well solved, it is ensured that the collection moment and displacement of each column of images are strictly synchronized, and the exposure time is constant.

Description

Technical Field

[0001] This invention relates to the field of signal generation technology, specifically a spatial curve triggered signal generation system based on a TDI line scan camera. Background Technology

[0002] In scanning systems based on TDI line scan cameras, ensuring image quality hinges on achieving precise synchronization between image acquisition and scanning displacement, while maintaining constant exposure conditions. To this end, existing technologies employ a displacement signal as the line trigger signal for the image acquisition system. Simultaneously, to ensure identical exposure time for each column, the TDI camera's movement speed must be stable during scanning.

[0003] In planar scanning systems, a single scanning axis typically drives the TDI camera in linear motion. A high-precision encoder on this scanning axis generates a fixed displacement increment signal (i.e., encoder pulse), which is directly used as the line trigger signal for the TDI camera. This method ensures that the camera moves a fixed distance for each frame of image data acquired. Simultaneously, by maintaining a stable speed along this single axis, the exposure time of each TDI camera step is kept consistent.

[0004] When the scanned surface is an irregular curved surface, the motion trajectory of the TDI camera changes from a one-dimensional straight line to a three-dimensional curve in space. This means that the camera needs to be driven collaboratively by three motion axes (e.g., X, Y, and Z axes) to accurately track the surface contour. This change introduces two key challenges:

[0005] 1. Increased Speed ​​Control Complexity: The composite linear velocity (i.e., the velocity along the tangent of the trajectory) of a TDI camera is no longer determined by the velocity of any single axis, but rather by the vector synthesis of the velocities of three axes. To ensure that this composite velocity remains constant, a high-performance multi-axis motion controller is required to calculate and precisely coordinate the motion of each axis in real time to cope with the dynamic effects caused by changes in trajectory curvature.

[0006] 2. Missing trigger signal source: In single-axis motion, the trigger signal can be directly provided by the encoder of that axis; however, in three-axis linkage, the total displacement of the camera is related to all linkage axes, and it is no longer possible to rely on the encoder signal of a single axis as a precise displacement interval trigger reference. Summary of the Invention

[0007] To address the problem that existing TDI line scan cameras cannot generate line trigger signals when performing spatial three-dimensional curve scanning, this invention proposes a spatial curve trigger signal generation system based on a TDI line scan camera.

[0008] This invention protects a spatial curve trigger signal generation system based on a TDI line scan camera, comprising:

[0009] The scanning control system is used to complete motion planning and fitting of three-dimensional spatial curves, and to send out the sequence of fitted line segments;

[0010] The straight line segment sequence processing unit is used to generate the encoder channel selection switch and straight line segment conversion coefficient Ki for each segment based on the fitted straight line segment sequence issued by the scanning control system.

[0011] A high-frequency clock generator is used to generate high-frequency clock signals as a reference clock for signal period measurement and signal generation.

[0012] The encoder signal multiplexing switch is used to select the corresponding encoder signal as the signal to be processed based on the encoder channel selection switch transmitted by the straight line segment sequence processing unit.

[0013] The period detection unit is used to sample the encoder signal at three different time points: T / 4, T / 2, and T, and output the period T of the encoder signal, where T is the reference clock period.

[0014] The interpolation compensation unit is used to calculate the period of the trigger signal using the period of the encoder signal and the straight segment conversion coefficient Ki, and then perform interpolation compensation to compensate for discrete errors.

[0015] The trigger signal generation unit is used to generate and output a trigger signal based on the trigger period signal output by the interpolation compensation unit.

[0016] In one embodiment of the present invention, the period detection unit includes:

[0017] The frequency multiplier is used to multiply the incremental encoder signal output through the encoder signal multiplexing switch, and output T / 4 latch signal, T / 2 latch signal and T latch signal respectively.

[0018] Three parallel sampling channels, including T / 4 channel, T / 2 channel and T channel, sample T / 4 latch signal, T / 2 latch signal and T latch signal respectively; each channel includes counter and latch, and timestamps are aligned through delay chain. The T / 4 channel and T / 2 channel also include multiplication operations of ×4 and ×2 respectively.

[0019] The priority selection trigger is used to determine the valid output of the current cycle based on the priority of the three parallel sampling channels and end the current query.

[0020] More specifically, the priority from highest to lowest is T / 4 channel, T / 2 channel, and T channel;

[0021] At the beginning of each cycle, the priority selection trigger starts checking the T / 4 channel. If the count value of the T / 4 channel changes, it immediately outputs the converted value of T / 4 channel × 4. If the T / 4 channel does not change, it checks the T / 2 channel. If the T / 2 channel changes, it outputs the converted value of T / 2 channel × 2. If neither the T / 4 channel nor the T / 2 channel changes, it finally checks the T channel and outputs its actual count value.

[0022] In one embodiment of the present invention, the interpolation compensation unit includes an ideal phase channel, an actual phase channel, a phase difference comparator, and an error compensation adder;

[0023] The ideal phase channel first passes through the first multiplier, then through the first accumulator, and performs a "+1" operation in each clock cycle T to achieve ideal phase accumulation; the actual phase channel first passes through the second accumulator to achieve speed feedback accumulation, and then through the second multiplier.

[0024] When the actual phase value output by the actual phase channel is greater than or equal to the ideal phase value output by the ideal phase channel, the phase difference comparator outputs a valid signal. This valid signal generates a trigger signal periodic pulse through the error compensation adder. At the same time, this valid signal is fed back to the first accumulator, causing the value of the first accumulator to be "+1".

[0025] This invention also protects a TDI line scan system for components with irregular curved surfaces, comprising:

[0026] TDI line scan camera, used to acquire surface images of components with irregular curved surfaces;

[0027] The scanning control system is used to plan the motor motion scheme and the three-dimensional space curve segment fitting scheme based on the three-dimensional model of the component to be detected. The motor motion scheme is sent to the multi-axis motion controller and the curve segment fitting scheme is sent to the space curve trigger signal generation system.

[0028] A multi-axis motion controller is used to control two camera adjustment motors and three scanning motors in conjunction with the motor motion scheme planned by the scanning control system.

[0029] A scanning motor is used to fit a spatial curve under the control of a multi-axis motion controller according to scanning requirements.

[0030] The camera adjustment motor is used to adjust the spatial attitude angle of the TDI line scan camera in real time under the control of the multi-axis motion controller according to the scanning requirements.

[0031] The aforementioned spatial curve trigger signal generation system is used to receive the encoder signal from the scanning motor and the curve fitting scheme issued by the scanning control system, generate a trigger signal and send it to the image acquisition system to achieve synchronous scanning of the spatial curve.

[0032] Image acquisition system for acquiring and processing image data from TDI line scan cameras.

[0033] In one embodiment of the present invention, the element having an irregular curved surface is an optical lens.

[0034] Based on a periodic detection unit and an interpolation compensation unit, this invention creatively proposes a spatial curve trigger signal generation system based on a TDI line scan camera. This system effectively solves the problem that existing TDI line scan cameras cannot generate line trigger signals when performing spatial three-dimensional curve scanning, ensuring that the acquisition time of each column of images is strictly synchronized with the displacement and that the exposure time is constant. Furthermore, this invention proposes a TDI line scan system with irregular curved surfaces. Attached Figure Description

[0035] Figure 1 This is a structural block diagram of the spatial curve trigger signal generation system based on a TDI line scan camera disclosed in Example 1;

[0036] Figure 2 This is a timing diagram of the incremental encoder signal;

[0037] Figure 3 This is a functional block diagram of the periodic detection unit;

[0038] Figure 4 This is a functional block diagram of the interpolation compensation unit;

[0039] Figure 5 This is a structural block diagram of the TDI line scanning system for components with irregular curved surfaces disclosed in Example 2. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0041] Example 1

[0042] A spatial curve trigger signal generation system based on a TDI line scan camera, such as Figure 1 As shown below, each module and its function will be introduced in detail.

[0043] The scanning control system 1 is used to complete motion planning and fitting of three-dimensional spatial curves, and to send out the sequence of fitted straight line segments.

[0044] The straight line segment sequence processing unit 2 is used to generate the encoder channel selection switch and straight line segment conversion coefficient Ki for each segment based on the fitted straight line segment sequence issued by the scanning control system.

[0045] Any three-dimensional curve in space is fitted by multiple continuous three-dimensional line segments in space. Assume the fitting points of the line segments for a three-dimensional curve are (X0, Y0, Z0), (X1, Y1, Z1), ..., (X... N Y N Z N The lengths of each corresponding straight line segment are L0, L1, ..., L. N-1 Then the conversion coefficients between the three directions and the three-dimensional line segments in space are Kx. i = (X i+1 -X i ) / L i K Yi =(Y i+1 -Y i ) / L i K Zi =(Z i+1 -Z i ) / L i The conversion factor for the straight line segment is K. i =max(K) Xi K Yi K Zi ),in ≤K i ≤1.

[0046] Within a straight line segment, the motion can be considered uniform; therefore, the ratio of the output line trigger signal period to the input encoder signal period is K. i K i The corresponding shaft encoder signal is used as the signal source for periodic detection and trigger signal generation.

[0047] High-frequency clock generator 3 is used to generate a high-frequency clock signal as a reference clock for signal period measurement and signal generation.

[0048] Encoder signal multiplexing switch 4 is used to select the corresponding encoder signal as the signal to be processed based on the encoder channel selection switch transmitted by the straight line segment sequence processing unit.

[0049] The period detection unit 5 is used to sample the encoder signal at three different time points: T / 4, T / 2, and T, and output the period T of the encoder signal, where T is the reference clock period.

[0050] The interpolation compensation unit 6 is used to calculate the period of the trigger signal by using the period of the encoder signal and the straight line segment conversion coefficient Ki, and to perform interpolation compensation to compensate for discrete errors.

[0051] The trigger signal generation unit 7 is used to generate and output a trigger signal based on the trigger cycle signal output by the interpolation compensation unit.

[0052] The following section will elaborate on the two most crucial components of the spatial curve trigger signal generation system: the period detection unit 5 and the interpolation compensation unit 6.

[0053] I. Periodic Detection Unit

[0054] The timing diagram of the incremental encoder signal is as follows: Figure 2 As shown, both channels A and B are rectangular wave signals with a duty cycle of 50% and a phase difference of 90°. The signal period T is obtained by counting the reference clock between adjacent rising edges in the same channel; the signal period T / 2 is obtained by counting the reference clock between adjacent falling edges in the same channel; and the signal period T / 4 is obtained by counting the reference clock between adjacent edges in both channels.

[0055] because If Ki ≤ 1, and only the entire cycle T is detected, the trigger signal will be delayed compared to the motion. Therefore, T / 2 or T / 4 must also be detected to correct the error step by step. Hence, the functional block diagram of the cycle detection unit is as follows: Figure 3 As shown.

[0056] The frequency multiplier is used to multiply the incremental encoder signal output through the encoder signal multiplexing switch, and output T / 4 latch signal (four times the frequency), T / 2 latch signal (two times the frequency), and T latch signal respectively.

[0057] Three parallel sampling channels, including T / 4 channel, T / 2 channel and T channel, sample T / 4 latch signal, T / 2 latch signal and T latch signal respectively; each channel includes a counter and a latch, and timestamps are aligned through a delay chain. The T / 4 channel and T / 2 channel also include multiplication operations of ×4 and ×2 respectively.

[0058] The periodic detection unit creates three "observation windows" at different phases / times:

[0059] 1. T / 4 latch signal: The first sample is taken at approximately 1 / 4 of the clock cycle.

[0060] 2. T / 2 latch signal: The second sample is taken at 1 / 2 of the clock cycle;

[0061] 3. T latch signal: The third (traditional) sampling is performed at the end of the clock cycle.

[0062] Delay chain: Figure 3 The purpose of the "delay" module in each sampling channel is to align the timestamps. Since the data sampled at T / 4 and T / 2 need to be processed uniformly in the subsequent processing, a precise delay line is required to ensure that the data captured at these three different times arrive at the subsequent processing circuit "logically" simultaneously for synchronous comparison and arbitration.

[0063] This embodiment, through the design of multi-phase sampling, enables the system to reduce the delay of effective position output from having to wait for the entire period T to an average of about T / 4, which significantly improves the real-time response capability of the system.

[0064] The priority selection trigger is used to determine the valid output of the current cycle based on the priority of the three parallel sampling channels and end the current query.

[0065] Three parallel sampling channels, each associated with a sampling time and assigned different "priorities". In this embodiment, priority 3 (highest) is associated with T / 4 sampling data, which represents the detection of the earliest stage of motion in the cycle; priority 2 is associated with T / 2 sampling data; and priority 1 (lowest) is associated with T sampling data, which is the latest and most traditional sampling point.

[0066] At the beginning of each cycle, the priority selection trigger starts checking the T / 4 channel. If the count value of the T / 4 channel changes, it immediately outputs the converted value of T / 4 channel × 4. If the T / 4 channel does not change, it checks the T / 2 channel. If the T / 2 channel changes, it outputs the converted value of T / 2 channel × 2. If neither the T / 4 channel nor the T / 2 channel changes, it finally checks the T channel and outputs its actual count value.

[0067] Operating logic: Each channel's "counter" records its frequency-multiplied count value at the corresponding sampling moment. The "latch" captures this value, and the system then checks whether the position counter has changed from the previous cycle to the current sampling point. Once a change is detected in the latch value of a channel (e.g., channel T / 4) relative to the previous final output value, it immediately adopts the data from that channel as the valid output for the current cycle and "resets" the entire query process. This means that the system will use the earliest sampled value from which motion change was detected whenever possible.

[0068] II. Interpolation Compensation Unit

[0069] Interpolation compensation unit such as Figure 4 As shown, it includes an ideal phase channel (upper path), an actual phase channel (lower path), a phase difference comparator, and an error compensation adder.

[0070] The ideal phase channel first passes through the first multiplier (×K) iThe first accumulator then performs a "+1" operation in each clock cycle T to achieve ideal phase accumulation. The ideal phase channel accumulates at a fixed frequency (system master clock), representing the ideal time base, with each accumulation step corresponding to one clock cycle.

[0071] The actual phase channel first passes through a second accumulator to achieve velocity feedback accumulation, and then passes through a second multiplier (×Ki). The actual phase channel accumulates based on the actual motion velocity, representing the true displacement phase, and its accumulation rate is proportional to the motion velocity.

[0072] When the actual phase value output by the actual phase channel is greater than or equal to the ideal phase value output by the ideal phase channel, it indicates that the actual motion has reached or exceeded the ideal position. Then, the phase difference comparator outputs a valid signal, which generates a trigger signal periodic pulse through the error compensation adder.

[0073] Simultaneously, the valid signal is fed back to the first accumulator, causing its value to increment by 1, meaning a phase value of one clock cycle is added to the first accumulator. This operation is equivalent to advancing the ideal phase forward by a full cycle, resetting the comparison state, and preventing error accumulation. Through this "trigger-and-compensate" mechanism, the difference between the actual phase and the ideal phase is always controlled within ±1 clock cycle, preventing the accumulation of errors.

[0074] Each time the phase difference comparator detects that the actual phase exceeds the ideal phase, it immediately generates a trigger signal periodic pulse. The time interval of this trigger signal periodic pulse is determined by the actual motion speed, but through a compensation mechanism, the long-term average frequency is locked at the ideal frequency.

[0075] This embodiment discloses a spatial curve trigger signal generation system based on a TDI line scan camera, which can solve the synchronization problem caused by multi-axis linkage speed fluctuations in the scanning system of a TDI line scan camera, ensuring that the acquisition time and displacement of each column of images are strictly synchronized, and the exposure time is constant.

[0076] Example 2: A TDI line scanning system for an element with an irregular curved surface, wherein the element can refer to any element with an irregular curved surface. Figure 5 The component with irregular curved surfaces is an optical lens.

[0077] TDI line scan cameras are used to acquire surface images of components with irregular curved surfaces.

[0078] The scanning control system is used to plan the motor motion scheme and the three-dimensional space curve segment fitting scheme based on the three-dimensional model of the component to be detected. The motor motion scheme is sent to the multi-axis motion controller, and the curve segment fitting scheme is sent to the space curve trigger signal generation system.

[0079] A multi-axis motion controller is used to control two camera adjustment motors and three scanning motors in conjunction with the motor motion scheme planned by the scanning control system.

[0080] A scanning motor is used to fit a spatial curve under the control of a multi-axis motion controller, according to scanning requirements.

[0081] The camera adjustment motor is used to adjust the spatial attitude angle of the TDI line scan camera in real time under the control of the multi-axis motion controller according to the scanning requirements.

[0082] The spatial curve trigger signal generation system disclosed in Example 1 is used to receive the encoder signal of the scanning motor and the curve fitting scheme issued by the scanning control system, generate a trigger signal and send it to the image acquisition system to realize synchronous scanning of spatial curves.

[0083] Image acquisition system for acquiring and processing image data from TDI line scan cameras.

[0084] Based on the spatial curve trigger signal generation system disclosed in Embodiment 1, this embodiment can perfectly realize TDI line scanning of optical lenses with irregular curved surfaces.

[0085] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A spatial curve trigger signal generation system based on a TDI line scan camera, characterized in that, include: The scanning control system is used to complete motion planning and fitting of three-dimensional spatial curves, and to send out the sequence of fitted line segments; The straight line segment sequence processing unit is used to generate the encoder channel selection switch and straight line segment conversion coefficient Ki for each segment based on the fitted straight line segment sequence issued by the scanning control system. A high-frequency clock generator is used to generate high-frequency clock signals as a reference clock for signal period measurement and signal generation. The encoder signal multiplexing switch is used to select the corresponding encoder signal as the signal to be processed based on the encoder channel selection switch transmitted by the straight line segment sequence processing unit. The period detection unit is used to sample the encoder signal at three different time points: T / 4, T / 2, and T, and output the period T of the encoder signal, where T is the reference clock period. The interpolation compensation unit is used to calculate the period of the trigger signal using the period of the encoder signal and the straight segment conversion coefficient Ki, and then perform interpolation compensation to compensate for discrete errors. The trigger signal generation unit is used to generate and output a trigger signal based on the trigger period signal output by the interpolation compensation unit.

2. The TDI line-scan camera-based spatial curve trigger signal generation system according to claim 1, wherein, The periodic detection unit includes: The frequency multiplier is used to multiply the incremental encoder signal output through the encoder signal multiplexing switch, and output T / 4 latch signal, T / 2 latch signal and T latch signal respectively. Three parallel sampling channels, including T / 4 channel, T / 2 channel and T channel, sample T / 4 latch signal, T / 2 latch signal and T latch signal respectively; each channel includes a counter and a latch, and timestamps are aligned through a delay chain. The T / 4 channel and T / 2 channel also include multiplication operations of ×4 and ×2 respectively. The priority selection trigger is used to determine the valid output of the current cycle based on the priority of the three parallel sampling channels and end the current query.

3. The TDI line-scan camera-based spatial curve trigger signal generation system of claim 2, wherein, The priority, from highest to lowest, is T / 4 channel, T / 2 channel, and T channel; At the beginning of each cycle, the priority selection trigger starts checking the T / 4 channel. If the count value of the T / 4 channel changes, it immediately outputs the converted value of T / 4 channel × 4. If the T / 4 channel does not change, it checks the T / 2 channel. If the T / 2 channel changes, it outputs the converted value of T / 2 channel × 2. If neither the T / 4 channel nor the T / 2 channel changes, it finally checks the T channel and outputs its actual count value.

4. The TDI line-scan camera-based spatial curve trigger signal generation system of claim 1, wherein, The interpolation compensation unit includes an ideal phase channel, an actual phase channel, a phase difference comparator, and an error compensation adder; The ideal phase channel first passes through the first multiplier, then through the first accumulator, and performs a "+1" operation in each clock cycle T to achieve ideal phase accumulation; the actual phase channel first passes through the second accumulator to achieve speed feedback accumulation, and then through the second multiplier. When the actual phase value output by the actual phase channel is greater than or equal to the ideal phase value output by the ideal phase channel, the phase difference comparator outputs a valid signal. This valid signal generates a trigger signal periodic pulse through the error compensation adder. At the same time, this valid signal is fed back to the first accumulator, causing the value of the first accumulator to be "+1".

5. A TDI line scan system having an element with an irregular curved surface, characterized in that, include: TDI line scan camera is used to acquire surface images of components to be inspected with irregular curved surfaces; The scanning control system is used for planning a motor motion scheme and a three-dimensional space curve segment fitting scheme according to a three-dimensional model of an element to be detected, sending the motor motion scheme to a multi-axis motion controller and sending the curve segment fitting scheme to a space curve trigger signal generation system, respectively; The multi-axis motion controller is used for linkage control of two camera adjustment motors and three scanning motors according to the motor motion scheme planned by the scanning control system; The scanning motor is used for fitting a space curve under the control of the multi-axis motion controller according to scanning requirements; The camera adjustment motor is used for real-time adjustment of a space posture angle of a TDI line scanning camera under the control of the multi-axis motion controller according to scanning requirements; The space curve trigger signal generation system according to any one of claims 1-4 is used for receiving an encoder signal of the scanning motor and the curve fitting scheme issued by the scanning control system, generating a trigger signal and sending the trigger signal to an image acquisition system to realize synchronous scanning of the space curve; The image acquisition system is used for image data acquisition and processing of the TDI line scanning camera.

6. The TDI line scan system with elements having irregular curved surfaces of claim 5, wherein, The element with an irregular curved surface is an optical lens.

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