RU2078364C1 - Device for photo detection of very-fast processes - Google Patents

Abstract

FIELD: optical devices for cinema and photography. SUBSTANCE: device has laser source 1, which is designed as gas laser, optical system which has diverging lens 4 and converging lens 5. Said optical system generates light beam 2. In addition device has photodetector 3. Laser source 1 is designed as ultraviolet nitrogen laser. Optical system which generates light beam 2 has ultraviolet light filters are located before photodetector 3. Device has luminescent screen 9 which shows picture. EFFECT: increased functional capabilities. 2 cl, 2 dwg

Description

 The device relates to the field of photographic registration of rapidly changing processes using lasers and obtaining tenegrams, heatgrams, holograms and interferograms and can be used in scientific and applied research, demonstration and educational processes.

A device is known that contains a light source in the form of pulsed solid-state or semiconductor lasers, an optical system that forms a light beam, and a photographic recorder [1]
One of the main disadvantages of devices using solid-state lasers is the low uniformity of the output beam due to the heterogeneity of the structure of the active element. A disadvantage of devices based on semiconductor lasers is the low brightness of the radiation with a large divergence.

 The closest technical solution to the invention is a device containing a pulsed laser source in the form of a copper vapor gas laser, an optical system that generates a light beam, and a photographic recorder [2] A pulsed gas vapor laser, in accordance with the characteristics of the generation conditions, provides pulses with a duration of ≈30 ns and wavelengths of 511 nm (green) and 578 nm (yellow).

 However, when photographing fast-changing and small-scale processes, these wavelengths and pulse durations are not always sufficient to obtain high image quality.

 An object of the invention is to improve image quality and resolution by reducing the wavelength and duration of the laser pulse.

 Another technical problem is the visualization of the invention.

 The technical result is achieved by the fact that the laser source is made in the form of an ultraviolet nitrogen laser, and the optical system that forms the light beam contains ultraviolet light filters installed in front of the photographic recorder along the beam propagation. In accordance with the generation conditions, a nitrogen laser provides pulses of ≲10 ns duration (in some cases up to picoseconds) with a wavelength of 337 nm (ultraviolet).

 To visualize the image, the optical system that forms the light beam is equipped with a luminescent screen installed after the ultraviolet light filters along the beam propagation.

 In FIG. 1 shows a general view of a device for photographing in ultraviolet rays; in FIG. 2 is a general view of a device equipped with a visualizing luminescent screen.

 The device for high-speed registration contains a pulsed laser ultraviolet light source, a nitrogen laser 1 (Fig. 1), an optical system forming a beam 2 and a photographic recorder 3.

 The optical system consists of scattering 4 and collecting 5 lenses (made of quartz transparent for ultraviolet radiation), as well as ultraviolet light filters 6, mounted in front of the photographic recorder 3 in the direction of beam propagation 2. Between the lenses there is an object for studying a cuvette 7 with water and mounted electrodes 8. For visualization image after ultraviolet light filters 6, along the propagation of the beam installed luminescent screen 9.

An example of a specific implementation. To conduct high-speed surveys of shock waves in a liquid, a laser device was used, containing one of the most low-power ultraviolet lasers, the LGI-21 laser in a single-pulse mode, triggered after the desired time interval from the start of the process under study, in our case, an electric discharge between electrodes 8 in a cell 7 with water. Laser data sheet 1: wavelength 337 nm, pulse duration 8 ns, power 3 kW, initial beam diameter 3 mm, divergence 3 • 10 ^-3 rad.

 The beam 2 from the laser 1 after the scattering lens 4 passed a cuvette 7 with water located at a distance of 2 m from the laser, was collected by the lens 5 and was recorded by the camera 3 with the lens removed (Fig. 1). Ultraviolet light filters 6 protected the camera film from exposure to the rays of the visible part of the spectrum.

 By changing the delay, studies were carried out at all stages of the repeating process. A clear picture was obtained on the technical films KN-4, RF-3, A-2 in the simple shadow mode without the use of a Temer's condenser using ray selection. In a diverging beam, it is possible to obtain images with an increase, in a converging beam with a decrease, such image transportation is very convenient. The transition to shorter wavelengths and shorter pulse durations of radiation makes it possible to improve the image quality by a factor of ten compared to the prototype, and to increase the resolution when photographing rapidly variable and small-scale processes.

So, for example, due to the brevity of the exposure, the image blur is equal to: Δx = v • τ,
where V is the speed of the process,
t exposure, reduced by tens of times.

And the resolution of the process details increases by 2 3 times due to a decrease in the diffraction angle: v = λ / d,
where λ is the wavelength
d characteristic dimensions of the image structure.

 The transition to the ultraviolet region of the spectrum provides a higher sensitivity of photographic recording, compared with visible light, for most photographic materials.

 Laser radiation itself is not visible to the human eye, but is perfectly recorded by film.

 Such radiation causes strong luminescence of even non-sensitized materials, which provides visualization of the image on the luminescent screen 9 (figure 2) when setting up the equipment, photo and filming, as well as for demonstration, educational and research purposes.

 A stable visualized image of the repeating processes was also obtained with the same delay between the start of the processes and laser flashes, which simplifies and facilitates the visualization and photographing of the process at all stages with a corresponding change in the delay.

 These methods of image accumulation also make it possible to reduce the required laser power by a factor of hundreds.

Claims (2)

 1. A device for photographic registration of rapidly changing processes, containing an ultraviolet pulsed laser source, an optical system that generates a light beam, an ultraviolet light filter and a photographic recorder, characterized in that the ultraviolet pulsed laser source is made in the form of a nitrogen laser, and an ultraviolet light filter is installed in front of the photographic recorder.  2. The device according to claim 1, characterized in that a luminescent screen is installed behind the ultraviolet light filter.

Images