RU2821221C1 - Digital system for synchronizing operating modes of elements of active optical imaging systems - Google Patents

Abstract

FIELD: image formation.

SUBSTANCE: invention relates to a digital system for synchronizing operating modes of elements of active optical imaging systems. System includes a mains filter, auxiliary power sources, an input pulse sequence processing unit, controls and high-speed microcontroller, which includes embedded software, which generates four sequences of output pulses with possibility of setting pulse duration and delay of pulse relative to input signal independently for each of four channels, which are fed to an output signal generating unit which generates optical pulses and electric pulses with adjustable amplitude from 0 to 15 V.

EFFECT: providing the possibility of synchronizing frequency-time parameters from two to four elements of active optical imaging systems with the possibility of independent adjustment of the actuation delay between them, as well as with possibility of control pulse amplitude adjustment.

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Description

The device belongs to digital electronics devices, namely to systems for generating digital pulses for controlling electronic devices. The device generates a pulse sequence synchronized with the input pulse sequence. The use of such a device is advisable in visualization systems based on optical-electronic amplifiers of optical signals for synchronizing the operating mode of the camera with the pulse-periodic operating mode of the amplifier, to ensure synchronization of the operating mode of several cameras, as well as for synchronizing several amplifiers of optical signals and a camera in a bistatic laser circuit monitor.

A device is known [Patent RU 185671 U1 High-voltage modulator] used to synchronize the operation of lasers in a laser monitor circuit. The device generates two high-voltage pulses with an adjustable time delay between them. A special feature of the device is the high accuracy of delay adjustment, which is 1 ns. This is achieved through the use of inductive delay lines. The disadvantage of the device is its large mass and dimensions due to the use of a thyratron as a key element, as well as inductive delay lines. In addition, the maximum time delay between two channels is limited by the selected inductances. The output signal levels do not allow the system to be used to synchronize the operating modes of digital cameras.

The famous work [F.A. Gubarev, A.V. Mostovshchikov, L. Li, High-speed optical imaging technique for combusting metal nanopowders, Optics & Laser Technology, Volume 159, 2023, 108981, ISSN 0030-3992, https://doi.org/10.1016/j.optlastec.2022.108981] , where the authors synchronized the operation of the brightness amplifier with two cameras. To regulate the time parameters of the delay between pulses and the duration of the synchronization pulses, an Aktakom AWG-4122 digital generator was used. The generator is equipped with two electrical outputs and is capable of generating a sequence of output pulses synchronized with the input sequence arriving at the electrical input. The advantage of the device is its availability and high accuracy of setting time parameters. The disadvantage is the response time (jitter) when using an external trigger pulse: the manufacturer claims a time of no worse than 380 ns, which is significant for synchronizing laser pulses with a duration of about 30 ns, which are typical for optical signal amplifiers based on gaseous media. In addition, the generator is not equipped with optical inputs and outputs, which may make it difficult to operate the device in environments with strong electromagnetic interference.

The device used in [N.] was chosen as a prototype. A. Vasnev, V. V. Taratushkina and M. V. Trigub, "Digital Control Circuit for Synchronization of Two Metal Vapor Lasers. Development and Application," 2018 19th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM), Erlagol, Russia, 2018 , pp. 6403-6406, doi: 10.1109/EDM.2018.8434987.]. The article presents the results of the development of a digital device for synchronizing the operating modes of two lasers. The device contains a surge protector, auxiliary power supplies, optical-to-electrical signal converters and controls. The executive element of the device is the Atmel Atmega 8A microcontroller, with an operating frequency of 16 MHz. The input command sequence of pulses arrives via an optical line, is converted into an electrical sequence and is sent to the corresponding pin of the microcontroller. The microcontroller generates two output signals with a given duration and delay relative to the input pulse sequence; these electrical signals are converted into optical signals and transmitted via optical lines to the appropriate devices. The disadvantage of the device is the large discreteness of setting the timing parameters - 1.5 μs, which depends on the speed of the microcontroller and the implemented software. Another disadvantage is the presence of two output channels with only optical outputs, which limits the range of connected devices. The absence of an indication block makes it difficult to configure the device.

The objective of the claimed invention is to form a sequence of optical and electrical pulses on four independent channels, synchronized with the input sequence of optical or electrical pulses, providing for adjustment of the amplitude of the output voltage of electrical pulses on each channel, the duration of the pulses on each channel, as well as a time delay relative to the input pulse for each channel, while the accuracy of timing parameters adjustment should be no worse than 5 ns.

The technical result consists in providing the ability to synchronize the time-frequency parameters of two to four elements of active optical visualization systems with the ability to independently adjust the response delay between them with an accuracy of setting the time parameters no worse than 5 ns, as well as with the ability to adjust the amplitude of control pulses in the range from 0 up to 15 V.

The technical result is achieved through the use of a high-speed STM32F767ZI microcontroller with a clock frequency of 216 MHz with built-in software, as well as developed independent output signal generation units that simultaneously generate optical pulses and electrical pulses with the ability to smoothly adjust the voltage in the range of 0-15 V.

The essence of the invention is that the digital synchronization system (Fig. 1) contains: a mains filter (1), auxiliary power supplies (2), an input pulse sequence processing unit (3), a microcontroller unit with specially designed software (4), display (6), controls (7) and four identical output signal generating units (5).

The input electrical or optical signal is supplied to the input pulse sequence processing unit (3). This block selects the input signal source using a quick switch of analog signals, converts the optical signal into an electrical signal, and also converts the input electrical signal to the level necessary for the correct operation of the microcontroller. Next, the signal goes to the microcontroller unit with built-in software (4). This block contains a high-speed STM32F767ZI microcontroller with a clock frequency of 216 MHz, passive components necessary for correct operation (resistors, capacitors), as well as additional digital devices: external SDRAM for correct operation of the display and non-volatile memory for the ability to save settings or recall default settings. The microcontroller generates four sequences of output pulses with the ability to configure the pulse duration and pulse delay relative to the input signal independently for each of the four channels. These signals are supplied to identical output signal generating units (5), in which the electrical signal is converted into an optical signal, as well as the amplitude of the output electrical signal is increased to a given value using boost converters. The device is configured using the controls (7) located on the front panel of the device next to the LCD display (6). To select a parameter to be adjusted, “Forward” and “Back” buttons are provided; an encoder is used to adjust the selected parameter. Also, to adjust the amplitude of the output signal in the range from 0 to 15 V, four knobs are provided on the front panel independently for each output channel (Fig. 2). The device is powered from a standard industrial network 220 V 50 Hz. An EMI filter (1) is provided to minimize electromagnetic interference. auxiliary power supplies (2) are converters of mains voltage into DC voltages of the required level for correct operation of the device.

The principle of operation of the synchronization system is as follows: after turning on the device, the microcontroller (4) loads the last saved parameters, including: the source of the reference (input) signal (optical or electrical), the frequency divider of the reference signal and pulse duration and delay for all four channels. All data is displayed on the display (6) and updated in real time. The input signal is processed in the input signal processing unit (3) and is fed to the microcontroller input. When a signal is received at the input, the microcontroller determines its frequency and displays the calculated value on the display, and also generates four signals with specified duration and delay parameters, which are sent to the output signal generating unit (5).

The algorithm of the program is presented in Fig. 3. The operating principle of the software is as follows. Each time you turn on, peripheral devices (8) are configured, including timers, data input/output ports, LTDC controller and FMC controller. After setting up the peripherals, the latest saved data is loaded from the EEPROM chip (M24C64) (9). This chip also stores the original values to reset the device to default settings. After data recovery, the controller begins to monitor the input pulse sequence and determines its frequency (10). By pressing the control buttons, you select the adjustable parameter (11), and then adjust it (12). Next, the controller checks whether the button to remember the current settings (13) was pressed. If the button has been pressed, the recording information (14) is displayed on the display and new data is written to the EEPROM chip (15). Then the data array is prepared for display and the display is updated (16). If the device is turned off (17), then the execution of the program code stops; if not, then the program returns to step (10) and all processes are repeated.

The LTDC controller provides image output to the display via a parallel RGB interface. The image on the display is formed from a data array that is stored in external SDRAM (IS42S16400J-7TLI) memory. Thanks to the use of the LTDC controller, the generation of control pulses to the display occurs at the hardware level and does not depend on the currently executing piece of software code. The task of the program code is to prepare a data array for subsequent display. The array is located in an external SDRAM chip, but due to the use of the FMC controller, the array in the external SDRAM is operated as with a regular internal memory array, and all control signals for the external memory are generated by the microcontroller in hardware.

The principle of generating synchronous pulses is based on the use of microcontroller timers in the mode of generating a single pulse. All timers of the microcontroller operate at a frequency of 216 MHz, which ensures the discreteness of adjustment of the pulse duration or pulse offset relative to the reference equal to 4.62 ns, taking into account external parasitic factors, the discreteness of adjustment is no worse than 5 ns (Fig. 3, Fig. 4). The input signal is supplied to the clock input of the first and second timers of the microcontroller. The first timer measures the frequency of the reference signal. The second timer is needed to divide the frequency of the reference signal. The output signal from the second timer is supplied to the inputs of four timers operating in the single-pulse generation mode. This signal is a trigger signal; after receiving this signal, the microcontroller will generate four output signals with programmable delay duration relative to the trigger signal and pulse duration.

The microcontroller program code prepares the array for displaying images, and also monitors controls and adjusts pulse durations. The pulse formation itself occurs at the hardware level, therefore, even with possible program failures, the pulse formation will continue with the last memorized settings. In addition, the entire process of generating output pulses occurs in a single digital device, this significantly increases noise immunity due to the lack of digital communication interfaces.

The device has small overall dimensions of 21x26x11 cm (LxWxH). Input and output connectors, as well as the power connector are located on the rear panel of the device. The front panel houses the display and controls.

Claims (1)

A digital system for synchronizing the operating modes of elements of active optical imaging systems, including a mains filter, auxiliary power supplies, an input pulse sequence processing unit and controls, an actuator - a microcontroller, characterized in that the high-speed microcontroller includes built-in software that generates four sequences of output pulses with the ability to adjust the pulse duration and pulse delay relative to the input signal independently for each of the four channels, which are supplied to the output signal generation unit, which generates optical pulses and electrical pulses with an adjustable amplitude from 0 to 15 V and the data is displayed on the display.