X-RAY TELEVISION INTROSCOPE SYSTEMS DEVELOPED AT NII EI IN 1969–1972

D. I. Sviryakin, A. N. Kolupaev,
V. F. Petushenko, V. I. Chantsev, A. D. Maksimenko

During 1969–1972, work continued at the Research Institute of Electronic Introscopy to improve methods of radiation introscopy. As a result, new systems of X-ray television introscopes were developed and introduced into production for monitoring the quality of welded and soldered joints, cast products made of aluminum and magnesium alloys, and the correctness of installation of electronic modules, as well as for observation and cine recording of dynamic processes occurring behind opaque barriers.

One of these systems is an X-ray television introscope introduced in 1972 for quality control of soldered joints in multilayer printed-circuit boards and for checking the correctness of assembly of radio-engineering modules. In addition to the main units that provide shadow X-ray black-and-white images, it contains a number of units and devices that improve the operator’s working conditions and increase the flaw-detection sensitivity of the introscope.

In contrast to the previously produced MTR-1 X-ray television microscope and the MTR-3 introscope currently being produced, the introscope created at NII EI can operate both with LI-417 and LI-423 X-ray vidicons; it has more powerful semiconductor scanning units, a low-noise camera video amplifier, an irradiation chamber several times larger in volume, a marker device for applying colored marks to defective areas, a conditional-coloring unit with a color video monitoring device, a system for local analysis of image brightness with recording of the analysis results on the chart tape of an automatic potentiometer, and a television monitor for photographing X-ray images on 35-mm photographic film.

The entire equipment complex of the introscope is shown in Figs. 1a and 1b. In Fig. 1a the units are arranged as follows (from left to right): the control panel of the RUP-150-10 apparatus; the device for X-ray irradiation of the inspected products with a manual manipulator located on the right side; in the foreground—the television-channel control panel; in the background—the transformer unit of the RUP-150-10 apparatus with a high-voltage cable; in the right-hand part of the irradiation device, on a rotating table, there is a black-and-white video monitoring device (VKU); to the right next to it is a stand with a color video monitoring device (TsVKU-1); then a cabinet with a sync generator, line- and frame-scan generators for the X-ray vidicons, an intermediate video amplifier, power-supply units, and a television mo-

Fig. 1a. Introscope for quality control of printed-circuit-board soldering

Fig. 1b. Unit for local brightness analysis of low-contrast images

with a monitor having a vidicon and a “Zenit” mirror photo camera. A sharp-focus X-ray tube of type 0.3BVP-6-150 with a focusing coil is located inside a lead protective casing and placed under the irradiation chamber. The decorative facing of the irradiation device conceals the casing with the X-ray tube and the collimator.

The X-ray vidicon (LI-417 or LI-423), with an FOS-35 focusing-deflection system, filament transformer, and preliminary video amplifier, is located beneath the irradiation chamber in a cylindrical housing lined on the inside with sheet lead. A special manual regulator makes it possible to change the distance from the center of the irradiation chamber to the input face of the X-ray vidicon. The design of the introscope and the protective devices completely eliminates the possibility of irradiating the operator and makes it possible to arrange all units of the introscope in one room.

The relative flaw-detection sensitivity provided by the introscope when operating with a black-and-white VCU lies within the range of 2–2.5% in copper equivalent at a thickness of 1.5–2 mm. The minimum diameter of a copper wire distinguishable on the VCU screen is 20 microns. When operating with the TsVKU-01, the sensitivity can be improved to 15%. This is explained by the fact that, in the conditional-coloring unit for the TsVKU image, which implements the frequency method of separating the video-signal spectrum into color channels, a transition is made from brightness contrast of image details to color contrast, which is more easily distinguished by the eye, and by the fact that, owing to the presence of three independent electron guns and the controllability of the degree of convergence of the beams of the color kinescope, it is possible to obtain the effect of subjective three-dimensionality, which helps in the visual extraction of image contours. In addition, visual analysis of color X-ray television images does not fatigue the flaw-detection operator as quickly as in the case of black-and-white images, which leads to an increase in the latter’s labor productivity.

Figure 1b shows an installation for local analysis of the brightness of low-contrast images. It contains an additional video monitoring device, a spatial selector with photodetectors connected according to a differential circuit, electronic image-shifting circuits, an amplification channel with an integrator, power-supply units, and a self-recording electronic potentiometer KSP-4. The position of the photodetectors over the image being analyzed is indicated at each moment by strobe pulses on the screen of the main black-and-white VCU. Analysis of the brightness of the image, and consequently of the density of the object being inspected, is carried out along a line crossing the image at any point and in any direction, with the photodetectors arranged in parallel or in series relative to the line of analysis. The position of the analysis line and the speed of image displacement are determined by the operator. The results of the analysis, in the form of a low-frequency analog signal, are recorded on the chart tape of the electronic potentiometer. Depending on the integration time, the speed of displacement of the image relative to the photodetectors, and the aperture of the latter, the contrast sensitivity of the introscope along the analysis line increases by a factor of 5–10, which makes it possible to detect defects that are not always revealed even by radiography. However, despite all these positive qualities, the described introscope is not and cannot be a universal installation, since the X-ray vidicons used in it have considerable inertia, a comparatively small area of X-ray-sensitive targets, and a narrow spectral range of recorded X-ray radiation (30–150 kV), which makes it necessary to inspect stationary articles of small thickness (6–8 mm for steel, 40–45 mm for aluminum) at a comparatively low productivity of inspection operations (0.005–0.1 m²/min).

Fig. 2a. Introscope for inspecting cast products

Higher productivity is provided by the introscope whose photographs are shown in Figs. 2a and 2b (the control panel for the RUP-120-5 X-ray apparatus is not shown here). On the front panel of Fig. 2a there is a general control console; on the rear panel is the VKU (black-and-white). In Fig. 2b there is a manipulator table with a duplicate control panel mounted on the left side; beneath the manipulator table is the X-ray receiver; on the table the item being inspected is fastened (a casting of the housing of a radio-electronic device); above the table, on a support with an electric drive, a transformer unit with the tube of the RUP-120-5 X-ray apparatus is installed, its radiation beam directed downward onto the item. The design of the introscope provides for its placement in two adjacent rooms—the control room (the general control console, the RUP-120-5 control panel, and the VKU) and the apparatus room (the radiation receiver, the manipulator table, and the stand with the radiation source). The manipulator table, equipped with an electric drive, has three degrees of freedom: rotation about an axis by ±45° and linear movement along two axes; therefore, during inspection of the item the operator is able to select the most advantageous angle of radiographic examination and, by scanning, to ensure inspection of the largest item (600 × 600 × 400)

Fig. 2b. Manipulator table

of aluminum and magnesium alloys with a total wall thickness of 80–90 mm.

The radiation receiver, unlike the one described earlier, has a larger X-ray-sensitive surface and lower inertia, but structurally it is considerably more complex. The functional diagram of the introscope with the structural diagram of the radiation receiver is shown in Fig. 3. Here the numeral 1 denotes the X-ray tube; 2—the cast body being inspected; 4—the X-ray electro-optical converter RU-135 (a schematic section is shown); 5—the transfer optics

Fig. 3. Functional diagram of an introscope with the structural diagram of the radiation receiver

image, consisting of two Jupiter-3 lenses combined with their input lenses; 6—the LI-421 vidicon; 7—the video amplifier; and 3—the black-and-white VCU, on which the operator observes the shadow X-ray image of the object under inspection. In domestic instrument engineering, such a radiation-receiver scheme had not previously been used, because of the comparatively low conversion factor of the RU-135 device and the poor light sensitivity of vidicons. Only the 1971–1972 production of RU-135 devices with high amplification factors (more than 3000) and of LI-422 and LI-421 vidicons operating at target illuminances of 2 and 1 lx, respectively, made it possible to implement this scheme. The flaw-detection sensitivity of the introscope is from 3 to 3.5% according to GOST 7512—69, and the resolving power is 1.8–2 line pairs/mm. It permits flaw detection of cast aluminum and magnesium products with a total wall thickness of up to 80 mm. The introscope circuit allows connection of a unit for local analysis of the brightness of images of the objects being inspected and a pseudo-coloring unit with a color VCU, which significantly expands the capabilities of the introscope. This introscope was introduced at one of the enterprises at the beginning of 1973.

The photograph in Fig. 4 shows an introscope intended for observation and motion-picture recording of dynamic processes occurring behind opaque barriers. In the center of the figure is the control console for all units; on the left is the stand of the motion-picture recorder, consisting of

Fig. 4. Introscope for observation and motion-picture recording of dynamic processes

a VK-150 video-monitoring device and a motion-picture camera with a lens barrel, equipped with an electric drive operating synchronously with the frame frequency; on the right is the main VK-12 video-monitoring device with, mounted on it during photography, a radiation receiver consisting of a scintillation single-crystal converter (or a polycrystalline thin-layer screen based on ZnS·CdS), image-transfer optics (an externally coated mirror, a Yu-9 lens with an auxiliary lens), and a transmitting television camera on an LI-218 superorthicon or a “Klubok” (or “Kvartet”) superisocon. The radiation source (not shown here) may be RUP-150-10 units,

RUP-120-5, RUP-200-5, etc. The choice of the transmitting television tube for the radiation receiver is determined by the characteristics of the dynamic process being recorded, by the thickness and material of the opaque shielding barriers, by the type of X-ray apparatus used, and by the parameters of the converting screen. The radiation source, the object under investigation, and the radiation receiver are located in a separate room, remote from the control room by a distance of up to 50 m. Motion-picture filming is carried out on 35-mm film, continuously or in short cycles, at a frequency of 25 frames/sec, with one of the television fields omitted (interlaced scanning). The moments at which filming begins and ends are determined by the operator, who observes the dynamic process under investigation on the screen of the main video-control unit. The layout of this introscope also permits connection of the pseudo-coloring unit and the color video-control unit. At the same time, without the motion-picture recorder, an introscope based on the RUP-150/300-10 apparatus and with a supericonoscope in the radiation receiver can be used for quality control of steel and cast-iron castings and welded seams in steel structures up to 50–60 mm thick. In this case, the flaw-detection sensitivity at optimal thicknesses of 20–40 mm lies within the range of 2.0–2.5% (GOST 7512—69), and the resolving power is 2–3 lines/mm, depending on the scintillation converter used. However, despite a certain advantage in sensitivity and resolving power, this introscope, in comparison with the preceding one, is more complex in its circuitry and is intended for operation under laboratory conditions. When a small-sized PMB-6 betatron, a 5-mm-thick CsJ (Tl) single-crystal screen, and a “Klubok” supericonoscope were used in the introscope, the thickness of the steel products being radiographed was increased to 70–80 mm. The flaw-detection sensitivity obtained with this version of the introscope, according to GOST 7512—55, was 1.5–2.0%, and the resolving power was 5–6 lines/mm.

From what has been said, it is clear that each of the introscopes described has its own field of application and cannot completely replace any other. Therefore, when choosing the type of X-ray television introscope, it is necessary to take into account not only the requirements imposed on its flaw-detection characteristics, but also the conditions in which the introscope will operate, the material, thickness, dimensions, and weight of the articles, the inspection productivity, the daily workload, and the level of technical maintenance.