RU2841288C1 - Laser projection system with double-channel image recording - Google Patents

Abstract

FIELD: quantum electronics.

SUBSTANCE: invention relates to quantum electronics and specifically to non-destructive inspection and diagnosis using optical methods. Laser projection system with two-channel recording comprises quantum amplifier on copper bromide vapour, lens for forming an optical image, a pumping system in the main and additional power supplies controlled by a high-voltage modulator and a programmable control board connected to a personal computer, according to invention time delay between generation of additional and main excitation pulses is 50-300 ns, amplitude of the main pulse is 1.5-2 times greater than the additional pulse and the formed optical intensified images are recorded by introduced image recording system consisting of photodetector, a pulse generator, a digital synchronization system and two machine vision cameras, which are interfaced with a personal computer.

EFFECT: formation of intensified images of a surveillance object.

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Description

The invention relates to the field of quantum electronics, namely to non-destructive testing and diagnostics using optical methods, and can be used to visualize test objects and fast-moving processes, including those shielded by broadband powerful background illumination.

A device for studying the combustion process of metal powders or their mixtures is known [Gubarev F.A., Li L., Mostovshchikov A.V., Ilyin A.P. Device for studying the combustion process of metal powders or their mixtures. Patent for invention No. 2685040. Date of state registration: 16.04.2019. Copyright holder: Federal State Autonomous Educational Institution of Higher Education "National Research Tomsk Polytechnic University"]. The device allows to simultaneously initiate the combustion process and obtain quantitative information on the time characteristics of the combustion processes of metal powders and their mixtures in real time. The temporal resolution of the system is limited by the pulse-periodic operating mode of the laser amplifier (20 kHz), and therefore there is no possibility of forming a sequence of two radiation pulses with a delay in the nanosecond range and their subsequent registration.

A device for visualizing objects and fast-flowing processes is known [Trigub M.V., Vasnev N.A., Evtushenko G.S., Dimaki V.A., Troitsky V.O. Bistatic laser monitor. Patent for invention No. 2755256. State registration date 09.14.2021. Copyright holder: IAO SB RAS (RU)], which contains two active elements and two power sources. The device ensures the registration of an image formed by a single illumination pulse and an amplified single amplification pulse, allowing the illumination and amplification parameters to be varied. However, the operating principle of this device is based on the coordination of the pulse-periodic operating modes of two active elements, the use of which allows to improve the quality characteristics of images and their numerical indicators, but not the temporal resolution of the system.

The work [Trigub M.V., Troitskii V.O., Dimaki V.A. Continuous control of CuBr laser pulse energy // Optics and Laser Technology - 2021. - Vol. 139, - P. 106929-1-106929-6. - DOI: 10.1016/j.optlastec.2021.106929] was chosen as a prototype, which presents a copper bromide vapor laser with the ability to control the energy of generation pulses by forming preionization pulses with an additional power source before the formation of excitation pulses by the main power source. The time delay between the preionization pulses and excitation pulses varied in the range of (0 ÷ 25) μs. With a time delay of (0.2 ÷ 2) μs, generation was completely suppressed. At a time delay of >2 μs, a yellow spectral line was generated, and at a time delay of >5 μs, a green spectral line was generated. This device allows regulating the average power (pulse energy) of laser radiation, but does not allow increasing the frame rate (temporal resolution) formed per unit of time by laser projection systems.

The problem solved by the invention: increasing the temporal resolution of a laser projection system for visualizing objects of observation in conditions of broadband powerful background illumination.

The specified problem is solved using a pumping system that forms two excitation pulses of a quantum amplifier with adjustable energy and time parameters and an image recording system consisting of two machine vision cameras, the operation of which is synchronized with the operation of the pumping system.

The technical result consists in the formation of enhanced images of the observation object with a time delay of (50÷300) ns and their registration using machine vision cameras, the operation of which is synchronized with the pumping system.

The technical result is achieved by means of a pumping system consisting of a control board, a high-voltage modulator, the main and additional power sources with adjustable energy and time parameters, the operation of which is synchronized with the image recording system consisting of a photodetector, a pulse generator, a digital synchronization system and two machine vision cameras that are interfaced with a personal computer. The main and additional power sources operate on one active element (quantum amplifier), as a result of which two pulses of amplified spontaneous emission are generated with a time delay in the range of (50÷300) ns, in each of which an amplified optical image of the observation object is formed.

The essence of the invention is that a personal computer, a programmable control board and a high-voltage modulator initiate the operation of the main and additional power sources in a pulse-periodic mode with adjustable energy and time parameters, as a result of which two excitation pulses (main and additional) of the quantum amplifier are formed, leading to the appearance of two pulses of amplified spontaneous radiation, which form amplified images of the observation object and are recorded by two independent machine vision cameras, coupled with a photodetector, a pulse generator, and a personal computer. The amplitude of the main excitation pulses should exceed the amplitude of the additional excitation pulses by (1.5÷2) times. The time delay between the radiation pulses corresponds to the time delay between the additional and main excitation pulses, which varies in the range of (50÷300) ns.

Thus, by coordinating the energy and time parameters of the power sources, as well as synchronizing the machine vision cameras, the formation and registration of enhanced optical images of the observation object occurs in each pulse. The time delay between the optical images corresponds to the time delay between the additional and main excitation pulses. The first camera records the image formed by the first radiation pulse, and the second camera records the image formed by the second radiation pulse, respectively.

The laser projection system with two-channel image registration and pumping system (Fig. 1) includes the following elements:

1 - active element on copper bromide vapor; 2 - objective; 3 - object of observation; 4 - translucent mirror; 5 - projection screen; 6, 7 - machine vision cameras; 8 - opaque mirror; 9 - photodetector; PC - personal computer; PU - programmable control board; VM - high-voltage modulator; IP1, IP2 - power supplies; GI - pulse generator; SS - digital synchronization system.

A laser projection system with two-channel image registration for visualization of observation objects shielded by broadband powerful background illumination contains an active element on copper bromide vapor (1), on the optical axis of which, on one side, a lens (2) and an observation object (3) are successively located. On the other side of the active element (1), on its optical axis, a semitransparent mirror (4) and a projection screen (5) are successively installed, in the plane of which a sharp, enhanced, enlarged image of the test object (process) of observation is formed.

A personal computer (PC) is used to configure the frequency-time parameters of the quantum amplifier (1) pumping (excitation) in the software. The set values of the frequency-time parameters are written to the control board (CP) of the pumping system (PS). The programmable control board (CP) generates a clock signal for the high-voltage modulator (HVM), which in turn generates two pulse trains initiating the operation of the additional (IP1) and main (IP2) power sources. Optical fiber is used to transmit each pulse train to the VM, IP1, and IP2 units. Optical transmitters, such as HFBR-1521Z, are used to convert electrical signals into optical signals. Fiber-optic receivers, such as HFBR-2521Z, are used for the reverse conversion. They are installed in the additional (IP1) and main (IP2) power sources, as well as in the high-voltage modulator (HVM).

The high-voltage modulator (HVM) also generates pulses to trigger the switches of the additional (IP1) and main power supply (IP2). The design and operating principle of the HVM are similar to the utility model [Vasnev N.A., Trigub M.V., Dimaki V.A., Evtushenko G.S., Troitsky V.O., Vlasov V.V. High-voltage modulator. Patent for utility model No. 185671. State registration date: 13.12.2018. Copyright holder: IAO SB RAS (RU)]. The pause between the additional and main excitation pulses is adjusted using variable inductances in the output time delay line of the HVM. Obviously, this leads to adjustment of the time delay between the radiation pulses that form the first and second optical images.

Two independent machine vision cameras (6, 7) are used to record images, for example, Baumer VLG-20C (27 fps) and JAI GO-5000C (3846 fps), controlled by a personal computer (PC). The exposure pulses of the high-speed cameras were synchronized with the radiation pulses. For this purpose, part of the radiation was diverted by a translucent (4) and opaque (8) mirror to a photodetector (9), for example, FEK-22-SPU-M. The output signal from the photodetector goes to the input of a pulse generator (PG), for example, G5-63. The output signal of the pulse generator (PG) initiated the operation of the digital synchronization system (SS), to the output channels of which the machine vision cameras (6, 7) are connected.

The laser projection system with two-channel image registration works as follows:

The additional power supply (IPS1) with a pulse charge of the working capacitor generates additional excitation pulses of the active medium (1) with a pulse repetition rate of (10÷12) kHz. The main power supply (IPS2) with a pulse charge of the working capacitor generates the main excitation pulses with a pulse repetition rate of (10÷12) kHz at (50÷300) ns later than the excitation pulses. The amplitude of the additional excitation pulses is set to be (1.5÷2) times smaller than the amplitude of the excitation pulses. The additional and main excitation pulses generate two pulses of amplified spontaneous emission with a time delay of (50÷300) ns relative to each other. The frequency-time parameters of the operation of the power supplies (IPS1, IP2) are set using a personal computer (PC), a control board (CP) and a high-voltage modulator (HVM).

The amplified spontaneous emission pulses reach the observation object (3) one by one, passing through the objective (2). The reflected emission pulses pass through the objective (2) again, forming an optical image of the observation object (3), and fall back into the medium of the active element (1), where they undergo spectral selective single-pass amplification. Then the amplified images reach the projection screen (5) one by one and are recorded by machine vision cameras (6, 7), controlled by a personal computer (PC). To trigger the camera shutter, part of the output radiation is diverted by the translucent (4) and blind (8) mirrors to the photodetector (9). The output signal of the photocell is a clock (reference) signal, which is fed to the input of the pulse generator (PG), for example, G5-63. The pulse generator (PG) forms a series of pulses of the required duration (1 μs) and amplitude (5 V) with a frequency equal to the frequency of the reference signal (10÷12) kHz. Such a series of pulses is fed to the input of the digital synchronization system (SS). Using the software and hardware of the synchronization system (SS), the frequency of the reference signal is reduced by a factor of 500. A sequence of pulses with a duration of 10 μs and an amplitude of 5 V with a frequency of 24 Hz is formed simultaneously on two output channels of the digital synchronization system (SS). Machine vision cameras (6, 7), for example, Baumer VLG-20C and JAI GO-5000C, are connected to the output channels of the digital synchronization system (SS). The time delay between the first and second series of synchronization pulses (input signals of the cameras) is regulated in a wider range than the radiation pulses, approximately (0÷500) ns - this makes it possible to record images at different moments in the existence of the signal carrying them. The output pulses (exposure pulses) of the machine vision cameras (6, 7) are formed at the moment of their shutters being triggered. The pulse duration corresponds to the specified exposure time of the shooting, which is set using a personal computer (PC). For the Baumer VLG-20C camera, the minimum exposure value is 4 µs, and for the JAI GO-5000C camera - 10 µs. In practice, the exposure duration can be increased if necessary, but for the implementation of frame-by-frame shooting, the exposure should not exceed the period, in this case (83÷100) µs.

The frequency-time modes of operation of the machine vision cameras (6, 7) were coordinated using a digital synchronization system developed on the basis of the STM32F767ZI microcontroller [Gembukh P.I., Trigub M.V., Vasnev N.A., Semenov K.Yu. Digital system for synchronizing the operating modes of elements of active optical imaging systems. Patent for invention No. 2821221. State registration date: 18.06.2024. Federal State Budgetary Scientific Institution Copyright holder: IAO SB RAS (RU)].

Fig. 2 shows the synchronization pulses (10, 11) and exposure pulses (12, 13) of the machine vision cameras. Between the synchronization pulses (10, 11) a time delay of 10 μs is set, significantly exceeding the delay in the nanosecond range, which is set during visualization - this is done in order to clearly demonstrate the synchronization and exposure pulses in one coordinate system.

Claims (1)

A laser projection system with two-channel registration, containing a quantum amplifier on copper bromide vapor, an objective for forming an optical image, a pumping system consisting of the main and additional power sources, controlled by means of a high-voltage modulator and a programmable control board connected to a personal computer, characterized in that the time delay between the formation of the additional and main excitation pulses is 50-300 ns, the amplitude of the main pulse is 1.5-2 times greater than the additional one, and the optical amplified images formed due to this are registered by the introduced image registration system, consisting of a photodetector, a pulse generator, a digital synchronization system and two machine vision cameras, which are interfaced with a personal computer.