JP5230282B2 - Nondestructive inspection equipment and nondestructive inspection methods - Google Patents

Description

  The present invention mainly relates to a nondestructive inspection apparatus and a nondestructive inspection method suitable for detection and analysis of scratches caused by cracks on a metal surface.

A flaw detector is used for nondestructive inspection of various metal products. In order to analyze the state of the flaw, a technique using image data acquired by photographing a flaw detection place has been developed (see Patent Document 1). Furthermore, in order to improve the quality of the photographed image, a technique using an ultraviolet light emitting diode as a light source has been developed (see Patent Document 2).
JP 2004-150908 A JP 2004-239749 A

Here, the conventional technique has the following problems to be solved.
Conventionally, an ultraviolet fluorescent tube or an ultraviolet light emitting diode has been used as a light source for a flaw detection test on a metal surface as in Patent Document 1 and Patent Document 2. The ultraviolet fluorescent tube has high brightness and can secure a sufficient amount of light. However, the ultraviolet fluorescent tube has a problem that it is difficult to miniaturize and is easily broken. For example, when inspecting a part of a large-sized device such as a vehicle, the flaw detection test device cannot be brought in. Therefore, the relevant portion of the vehicle must be disassembled and set in the flaw detection test device.

Ultraviolet light emitting diodes can be reduced in size and weight, and have excellent mobility. That is, there is an advantage that the degree of freedom is high, and the inspection can be performed directly by bringing it into a large-sized device such as a vehicle. However, there is a problem that it is difficult to obtain a sufficient amount of light. In any case, since the phosphor attached in the vicinity of the portion to be imaged is emitted and observed with the naked eye, it is difficult to observe the test object when affected by extraneous light. Therefore, there has been a problem that preparation work such as turning off ambient lighting or installing a black curtain is required.
An object of this invention is to provide the nondestructive inspection apparatus and nondestructive inspection method which solve the above subject.

In each embodiment of the present invention, the above-described problems are solved by the following configurations.
<Configuration 1>
The light source of an ultraviolet light emitting diode that irradiates pulsed ultraviolet light on the surface of the subject with the phosphor attached in the vicinity of the object to be photographed, and the exposure operation are periodically repeated, and the image signal on the surface of the subject is obtained frame by frame. A synchronization control circuit that extracts a synchronization control signal from a camera to be acquired and generates an ultraviolet light emission control signal used for light emission control of the ultraviolet light emitting diode is provided, the ultraviolet light emission control signal from the start time T1 of the exposure operation The control signal for starting the irradiation of the ultraviolet light by the ultraviolet light emitting diode just before the time t2 and ending the irradiation of the ultraviolet light after the end time T2 of the exposure operation, wherein the synchronization control circuit The exposure operation is started at a timing when the brightness of the phosphor becomes higher than the surrounding after the start of irradiation of the ultraviolet light on the surface. Stores the measured value of the time t2, the nondestructive inspection device and generating the ultraviolet light emission control signal.

  Since the pulsed ultraviolet light is irradiated using the light source of the ultraviolet light emitting diode, it is possible to irradiate the powerful ultraviolet light. Since the exposure is performed for a predetermined time after the start of ultraviolet light irradiation on the surface of the subject and the brightness of the phosphor becomes higher than the surroundings, it is possible to take a picture at the timing when the subject emits light clearly. Further, since the exposure is completed before the start of the ultraviolet light irradiation end, it is not affected by disturbance light after necessary image data acquisition.

<Configuration 2>
2. The nondestructive inspection apparatus according to Configuration 1, wherein the phosphor is substantially uniformly attached to and around the imaged portion of the subject surface.

  Since the fluorescent substance is almost uniformly attached to the portion to be photographed on the surface of the subject and the periphery thereof, the main part of the subject can be clearly photographed.

<Configuration 3 >
A light source of an ultraviolet light emitting diode that irradiates pulsed ultraviolet light is disposed on the surface of the subject with a phosphor attached in the vicinity of the object to be photographed , and the exposure operation is periodically repeated by the synchronous control circuit for each frame. A synchronization control signal is extracted from a camera that acquires an image signal of the surface of the subject, and an ultraviolet light emission control signal used for light emission control of the ultraviolet light emitting diode is generated. The ultraviolet light emission control signal is the start time T1 of the exposure operation. The control signal for starting the irradiation of the ultraviolet light by the ultraviolet light emitting diode before the time t2, and ending the irradiation of the ultraviolet light after the end time T2 of the exposure operation. The exposure operation is started at the timing when the luminance of the phosphor becomes higher than the periphery after the irradiation of the ultraviolet light on the subject surface is started. By storing the measured values of the time t2, the non-destructive inspection method, characterized in that to generate the ultraviolet light emission control signal.

<Configuration 4 >
7. The nondestructive inspection method according to Configuration 6, wherein the fluorescent material is substantially uniformly attached to a portion to be photographed on the surface of the subject and the periphery thereof.

(1) Since pulsed ultraviolet light is irradiated by an ultraviolet light emitting diode, ultraviolet light having a high energy density can be generated.
(2) Since the fluorescent material attached in the vicinity of the imaging location is caused to emit light and the imaging location is photographed for a predetermined time when the maximum luminance is exhibited, the influence of external light or the like is small. Therefore, it is possible to perform a flaw detection inspection of an object clearly even in a place where the surroundings are relatively bright without preparation of a dark screen or the like.
(3) When the ultraviolet light emitting diode is driven by a portable power source such as a battery, a device that can be reduced in size and weight and has excellent mobility can be provided.

  Hereinafter, embodiments of the present invention will be described in detail for each example.

FIG. 1 is a schematic configuration diagram of a nondestructive inspection apparatus 10 of the present invention.
The nondestructive inspection apparatus 10 includes a light source 15 using an ultraviolet light emitting diode 14, a camera 16, a power supply 18, and a synchronization control circuit 20. A phosphor 22 is attached in the vicinity of the shooting location of the subject 12. The light source 15 irradiates the surface of the subject 12 with pulsed ultraviolet light. In the following embodiment, an eddy current is generated by an electromagnet or the like (not shown), and the phosphor 22 penetrates the scratches on the surface of the subject 12 evenly. The camera 16 is a video camera. A video signal obtained by photographing with the camera 16 is transferred to the video monitor 30.

FIG. 2 is a circuit block diagram of the nondestructive inspection apparatus 10 of the present invention. FIG. 3 is a cross-sectional view of the vicinity of the surface of the subject 12.
The camera 16 receives a light image of the subject 12 through an ultraviolet filter 36 and an optical lens 38 that block ultraviolet rays. For the camera 16, for example, a CCD device is used. As shown in FIG. 3, the phosphors 22 are almost uniformly attached to the area to be photographed on the surface of the subject 12 and the vicinity thereof. If there is a flaw in the portion to be photographed, the phosphor 22 also enters the inside of the flaw. When the ultraviolet light is irradiated from the light source 15, the phosphor 22 emits light, and the entire portion to be photographed emits light, so that a clear image can be taken. Since the CCD of the camera 16 has a certain sensitivity in the ultraviolet region, the emission of the phosphor becomes clearer by cutting the ultraviolet region using the ultraviolet filter 36.

FIG. 4 is an exposure control timing chart by the above camera.
The camera 16 performs exposure control by opening a shutter (not shown) between times T1 and T2. The shutter controls to receive the optical image of the subject 12 through the optical lens 38 only during the time T1 to T2. The shutter may be a liquid crystal shutter that physically blocks light input to the CCD device, or a control circuit that electrically controls the effective exposure time of the CCD device. The pulse width of the exposure control signal 51 is time t1.

  The camera 16 periodically repeats the exposure operation described above to acquire the subject image signal for each frame. The video signal is a signal for continuously outputting the image signal at a predetermined cycle. The camera uses the synchronization control signal 52 for frame transfer control of the video signal. The synchronization control circuit 20 extracts the synchronization control signal 52 from the video signal and generates a trigger timing signal 53 used for light emission control of the ultraviolet LED. A general still camera requires a complicated control circuit for synchronization with a shutter. In the video camera, since the synchronization control signal 52 can be automatically extracted from the video signal, there is an effect that the synchronization control can be easily performed without any additional work on the camera side.

  The trigger timing signal 53 is a pulse signal that rises at the fall timing (time T4) of the synchronization control signal 52 and becomes high level for a unit time. The polarity of each pulse signal described in this embodiment can be arbitrarily selected according to the circuit design.

  The synchronization control circuit 20 generates the delayed trigger signal 54 by delaying the trigger timing signal 53 by t4 time. The rise time T0 of the delay trigger signal 54 is set to be a time t2 before the camera exposure start time T1. The ultraviolet light emission control signal 55 is a pulse signal that rises at the rise timing (time T0) of the delay trigger signal 54 and has a time width t3. The ultraviolet light emission control signal 55 falls after the rising time T2 of the exposure control signal 51. While the ultraviolet light emission control signal 55 is at a high level, electric power for causing the ultraviolet LED to emit light is supplied. By this control, the time during which the ultraviolet LED emits light becomes longer than the exposure time, and t1 <t3. The phosphor emission intensity 56 changes as shown in the figure. Even if the phosphor emits light, if the surrounding area is brighter, clear photographing cannot be performed. A broken line K indicates the brightness level of the surroundings. When the brightness of the phosphor is higher than the surroundings, the image of the subject appears clearly. Exposure may be started at this timing, and then exposure may be performed for a predetermined time required for photographing. The exposure time may be selected according to the sensitivity of the CCD device and the light emission intensity of the ultraviolet LED. When actual values are calculated by actual measurement and stored in the control circuit, control is possible at this timing.

FIG. 5 is an explanatory diagram showing changes in the light emission time of the ultraviolet light emitting diode 14 and the light emission intensity of the phosphor.
The time G for causing the ultraviolet light-emitting diode 14 to emit light is preferably 100 μsec or more and 3 msec or less. If the light emission time G is less than 100 microseconds, sufficient electrical energy cannot be supplied to cause the ultraviolet light emitting diode 14 to emit light. On the other hand, if the light emission time G exceeds 3 milliseconds, due to the characteristics of the ultraviolet light-emitting diode 14, light must be emitted with low luminance, and the phosphor cannot be emitted with high luminance. In addition, the exposure time of the camera becomes longer, and accordingly, it is more susceptible to extraneous light. If the time for controlling the current to flow becomes too long, it will not change from continuous lighting. It is preferable to emit light with a pulse width that does not lose the significance of strobe light emission.

  As shown in FIG. 5, there is a limit to the amount of electric energy supplied to cause the ultraviolet light emitting diode 14 to emit light. As shown in FIG. 5A, if the light emission time is short, light can be emitted with high luminance. At this time, the phosphor emits light with high luminance. As shown in FIG. 5B, when the light is emitted for a long time, the luminance must be lowered. At this time, the light emission luminance of the phosphor is lowered. In order to cope with the above problems, the ultraviolet light emission time G is set to 100 μsec or more and 3 msec or less.

FIG. 6 is an explanatory diagram of the effect of the filter.
The ultraviolet rays emitted from the ultraviolet light emitting diode irradiate the subject 12. The phosphor 22 absorbs the ultraviolet rays and emits light strongly. The camera 16 captures this visible light. Therefore, the incidence of ultraviolet rays that can affect the captured image is eliminated. At the same time, visible light from external light is also reflected from the subject. However, as described above, since the exposure is controlled only when the phosphor emits light brighter than the surroundings, only the light necessary for clear photographing of the subject can be input to the camera side.

FIG. 7 is a flowchart of the work procedure of the entire nondestructive inspection work.
This shows the work procedure of the person in charge who performs the nondestructive inspection. First, in step S11, preparation for installation of an inspection object is performed. For example, the subject surface is cleaned to prepare the shooting environment. Next, in step S12, the phosphor is sprayed on the inspection target. Further, an eddy current generation process is performed in step S13. As a result, the phosphor adheres to the vicinity of the shooting location of the subject until it reaches the inside of the scratch. That is, the state shown in FIG. 3 is obtained.

  In step S14, the subject is irradiated with ultraviolet rays by the apparatus shown in FIG. In step S15, the subject is photographed by the camera. The operation of steps S14 and S15 will be described in detail with reference to FIG. In step S16, the video monitor is monitored. In step S17, the photographed image is evaluated. In step S18, it is determined whether an optimal image has been acquired. If the result of this determination is yes, the operation is terminated. If no, the process returns to step S14, and the photographing of the subject by the camera is repeated.

FIG. 8 is an operation flowchart of the nondestructive inspection apparatus of the present invention.
This process is automatically executed inside the nondestructive inspection apparatus. First, in step S21, the power of the nondestructive inspection apparatus is turned on. In step S <b> 22, the camera 16 starts operating and outputs a video signal to the video monitor 30. This signal is also sent to the synchronization control circuit 20 side. In step S23, the synchronization control circuit 20 extracts the synchronization control signal 52. In step S24, the synchronization control circuit 20 generates the trigger timing signal 53. Next, the synchronization control circuit 20 delays the trigger timing signal 53 by a set time in step S25, and generates a delayed trigger signal 54 in step S26. Further, an ultraviolet light emission control signal 55 is generated in step S27.

  The synchronization control circuit 20 supplies this signal to the light source 15 and drives the ultraviolet light emitting diode 14 in step S28. In step S29, the camera 16 performs an exposure operation at the timing shown in FIG. 4 and acquires an image signal. The camera 16 transfers the captured video signal to the video monitor 30 in step S30. In step S31, it is determined whether or not the apparatus is turned off. If the result of this determination is yes, the process is terminated, and if no, the process returns to step S22 and the operations of steps S22 to S30 are repeated again.

  As described above, since the light emitting operation of the ultraviolet light emitting diode 14 and the exposure operation of the camera 16 are synchronized, the fluorescent material soaked into the wound is emitted by the eddy current processing, and an image of the subject is photographed at the optimum timing. it can. The camera 16 captures visible light emitted from the wound on the metal surface, but at the same time, ultraviolet light is also reflected from the metal surface. Therefore, a filter that blocks ultraviolet rays was used. In addition, if exposure is performed outside the time during which the phosphor is effectively emitting light, the incident ratio of unnecessary extraneous light increases, and the S / N ratio (signal-to-noise ratio) deteriorates. For this, the camera is exposed for the minimum necessary time. In this way, optimal flaw detection can be performed. Usually, such a flaw detection inspection is performed by using a dark screen or the like in consideration of the behavior of the fluorescent paint with respect to ultraviolet rays. In bright outdoor places where sunlight enters, extraneous light such as visible light is so large that it is difficult to see the light of the fluorescent part.

  When the object is irradiated with a light source that is continuously lit and photographed with a camera, the contrast deteriorates. The contrast deteriorates even when taken in a bright place. In the apparatus of the present invention, since the light-emitting diode emits light strongly for a short time to supply a large amount of light energy to the phosphor, and photographing is performed when the phosphor emits light at the maximum luminance, the contrast is very good. Since the object to be photographed using the camera is a phosphor, it is possible to prevent extra light from being inserted into the camera from around. When it is outdoors, it is about 100,000 looks in direct sunlight. It will be around 10,000 looks in the sun. However, the brightness is reduced to one-tenth or less in shaded or cloudy conditions. In the present invention, there is an effect that photographing with a sufficiently high S / N ratio can be performed to the extent that it is shaded while avoiding direct sunlight.

It is a schematic block diagram of the nondestructive inspection apparatus of this invention. It is a circuit block diagram of the nondestructive inspection device of the present invention. It is a cross-sectional view of the vicinity of the surface of the subject. It is an exposure control timing chart by a camera. It is explanatory drawing which shows the change of the light emission time of the ultraviolet light emitting diode 14, and the emitted light intensity of a fluorescent substance. It is an effect explanatory view of a filter. It is a flowchart of the work procedure of the whole nondestructive inspection work. It is an operation | movement flowchart of the nondestructive inspection apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Nondestructive inspection apparatus 12 Subject 14 Ultraviolet light emitting diode 15 Light source 16 Camera 18 Power supply 20 Synchronization control circuit 22 Phosphor 24 Optical system 26 DC / DC converter 28 Battery 30 Video monitor 36 Ultraviolet filter 38 Lens 51 Exposure control signal 52 Synchronization control signal 53 Trigger timing signal 54 Delay trigger signal 55 Ultraviolet light emission control signal 56 Phosphor emission intensity

Claims (4)

A light source of an ultraviolet light emitting diode that irradiates a pulsed ultraviolet light on the surface of a subject to which a phosphor is attached in the vicinity of a shooting location;
Synchronously generating an ultraviolet light emission control signal used for light emission control of the ultraviolet light emitting diode by periodically repeating an exposure operation to extract a synchronization control signal from a camera that acquires the image signal of the subject surface for each frame. Equipped with a control circuit,
The ultraviolet light emission control signal starts irradiation of ultraviolet light by the ultraviolet light emitting diode before time t2 from the start time T1 of the exposure operation, and ends irradiation of the ultraviolet light after the end time T2 of the exposure operation. Control signal
The synchronization control circuit stores an actual measurement value of the time t2 such that the exposure operation is started at a timing when the luminance of the phosphor becomes higher than the periphery after the irradiation of the ultraviolet light on the subject surface is started. A non-destructive inspection apparatus for generating the ultraviolet light emission control signal .   The nondestructive inspection apparatus according to claim 1, wherein the phosphor is substantially uniformly attached to and around the object to be imaged on the surface of the subject. Place the light source of the ultraviolet light emitting diode that irradiates the pulsed ultraviolet light on the subject surface with the phosphor attached in the vicinity of the shooting location,
An ultraviolet light emission control signal used for light emission control of the ultraviolet light emitting diode by extracting a synchronization control signal from a camera that acquires an image signal of the subject surface for each frame by periodically repeating an exposure operation by a synchronization control circuit. Produces
The ultraviolet light emission control signal starts irradiation of ultraviolet light by the ultraviolet light emitting diode before time t2 from the start time T1 of the exposure operation, and ends irradiation of the ultraviolet light after the end time T2 of the exposure operation. Control signal
The synchronization control circuit stores an actual measurement value of the time t2 such that the exposure operation is started at a timing when the luminance of the phosphor becomes higher than the surrounding after the irradiation of the ultraviolet light on the subject surface is started. A nondestructive inspection method characterized by generating the ultraviolet light emission control signal . The nondestructive inspection method according to claim 3, wherein the phosphor is substantially uniformly attached to a portion to be photographed on the surface of the subject and the periphery thereof.

Images