RU2841276C1 - Method of viewing surveillance objects using laser projection system with two-channel recording - Google Patents

Abstract

FIELD: quantum electronics.

SUBSTANCE: invention relates to quantum electronics and specifically to non-destructive inspection and diagnosis using optical techniques. Method of imaging objects shielded by a broadband powerful backlight, based on pumping a quantum amplifier on copper bromide vapour with main and additional high-voltage excitation pulses generated by two power sources, amplified spontaneous radiation pulses focusing on the observation object by the lens and the optical images formation with its help, their projection on the screen after the amplification by the quantum amplifier, differs in that additional pumping source generates additional active medium excitation pulse, then after a time delay of 50-300 ns, the main power supply generates the main excitation pulse of the active medium, the amplitude of which is 1.5-2 times higher than the amplitude of the additional pulse, and two computer-controlled machine vision cameras record images formed by two radiation pulses.

EFFECT: generation of two pulses of amplified spontaneous radiation.

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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 method for studying the combustion process of a mixture of coarse metal powders is known [Evtushenko G.S., Trigub M.V., Gubarev F.A., Evtushenko T.G., Torgaev S.N., Shiyanov D.V. Laser monitor for non-destructive testing of materials and processes shielded by intensive background lighting // Review of Scientific Instruments - 2014. - Vol. 85. - Issue 3. - P. 154-159. - DOI: 10.1134/S102485602102010X], which includes focusing the amplified spontaneous radiation of a quantum amplifier on the object of study, forming an image using an optical system, amplifying the image in an active medium and projecting it onto a high-speed CCD camera. The CCD camera exposure is synchronized with the quantum amplifier superluminosity pulse, which ensures frame-by-frame registration of the process (image registration in each pulse). However, the quantum amplifier is excited by one power source and operates in the traditional pulse-periodic mode in the frequency range (20÷25) kHz, which eliminates the possibility of forming two frames with a time delay in the nanosecond range.

A method for studying the combustion process of metal powders or their mixtures is known [Gubarev F.A., Li L., Mostovshchikov A.V., Ilyin A.P. Method for studying the combustion process of metal powders or their mixtures. Patent for invention No. 2685072. State registration date: 16.04.2019. Copyright holder: Federal State Autonomous Educational Institution of Higher Education "National Research Tomsk Polytechnic University"]. The method allows igniting metal powders and studying the processes of their combustion, as well as the processes of interaction of laser radiation with matter. However, the shooting speed is also limited by the pulse-periodic mode of operation 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.

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 generating preionization pulses by an additional power source before generating excitation pulses by the main power source. The time delay between the preionization pulses and the 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, the generation of a yellow spectral line appeared, and at a time delay of >5 μs, the generation of a green spectral line also appeared. The described control method allows regulating the average power (pulse energy) of laser radiation, but does not allow increasing the frequency of frames 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 observation objects under conditions of broadband powerful background illumination.

The specified problem is solved by forming two excitation pulses of the quantum amplifier (main and additional) with a time delay in the range of (50÷300) ns.

The technical result consists in generating two pulses of amplified spontaneous radiation with an adjustable time delay in the range of (50÷300) ns, forming amplified images of the observation object and recording each of them using a separate machine vision camera.

The technical result is achieved by coordinating the frequency-time and energy parameters of the main and additional power sources, as well as synchronizing the exposure pulses of two independent machine vision cameras with pulses of amplified spontaneous emission.

The essence of the invention lies in the fact that the quantum amplifier is pumped by two power sources in such a way that first the additional power source forms an additional excitation pulse of the active medium of the quantum amplifier (active element), as a result of which the first radiation pulse is generated, then, after a time delay of (50÷300) ns, the main power source forms the main excitation pulse of the active medium of the quantum amplifier (active element), the amplitude of which is higher than the amplitude of the preionization pulse by (1.5÷2) times, which leads to the generation of the second pulse of amplified spontaneous emission. Thus, due to different energy parameters of the additional and main excitation pulses, two pulses of amplified spontaneous emission are alternately formed in the active medium of the quantum amplifier. The time delay between the radiation pulses corresponds to the time delay between the additional and main excitation pulses. The formation of two pulses in a row occurs only in the range of the time delay of (50÷300) ns. In Fig. 1. An example of oscillograms of excitation pulses (additional - U1, main - U2) and amplified spontaneous emission (L1, L2) is presented. The example is presented for a time delay of tз=86 ns.

Each pulse of amplified spontaneous emission illuminates the object of observation, which can be screened by broadband powerful background illumination, forms an optical image of the object using a lens, in the active medium of the amplifier there is an increase in brightness (spectral selective amplification) of the image projected onto the screen, and then the images are alternately recorded by two machine vision cameras with an adjustable delay of the exposure pulses (the moment of frame formation) relative to the pulses of amplified spontaneous emission.

The presented method proposes to form two excitation pulses of the active medium with a small time delay relative to each other, which is an atypical mode of pumping the active medium (active element) of a quantum amplifier on copper bromide vapor. An additional power source (APS1) forms additional excitation pulses, the main power source (MPS2) forms the main excitation pulses of the active medium.

The visualization method and the laser projection system with two-channel registration that implements it are shown in Fig. 2.

The method of visualizing objects and fast-flowing processes, screened by broadband powerful background illumination, is implemented using a laser projection system, which contains an active element on copper bromide vapor (1), on the optical axis of which, on one side, an objective (2) and a test object (process) of observation (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 object of observation is formed.

For two-channel recording of images of the observed objects, two independent machine vision cameras (6, 7) are used, 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 using a translucent (4) and a opaque (8) mirror to a photodetector (9), for example, FEK-22-SPU-M. The output signal from the photodetector goes to the input of the 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.

Claims (1)

A method for visualizing objects shielded by broadband powerful background illumination, based on pumping a quantum amplifier on copper bromide vapor with the main and additional high-voltage excitation pulses formed by two power sources, focusing the pulses of amplified spontaneous radiation on the object of observation by the lens and forming optical images with its help, projecting them onto a screen after amplification by the quantum amplifier, characterized in that the additional pump source forms an additional excitation pulse of the active medium, then after a time delay of 50-300 ns the main power source forms the main excitation pulse of the active medium, the amplitude of which is higher than the amplitude of the additional pulse by 1.5-2 times, and two machine vision cameras controlled by a personal computer record the images formed by the two radiation pulses.