JP6332001B2 - High speed photography system - Google Patents

Description

  The present invention relates to a high-speed photographing system for photographing a high-speed phenomenon.

A metal transforms into various phases depending on temperature, pressure, and the like. By correctly knowing conditions such as temperature and pressure of these phase transformations, the metal can be used under optimum conditions.
For example, in the case of carbon steel, when it is heated, the ferrite pearlite structure near room temperature becomes an austenite structure at about 800 ° C., and it becomes a very hard martensite structure by quenching (quenching) from that state. These structural changes (phase transformations) appear very rapidly, depending on the rate of temperature change.

  In order to capture such a high-speed phenomenon, a dedicated high-speed video camera has been developed (Patent Document 1, Non-Patent Documents 1 and 2). For example, the high-speed video cameras described in Non-Patent Documents 1 and 2 are equipped with an image sensor with a special structure called a pixel peripheral recording image sensor (IS-CCD = image storage-CCD). Very high-speed shooting of frames / second (1 Mfps, that is, 1 μsec / frame) is possible.

A high-speed video camera has a high shooting speed, but cannot take a long recording time. For example, in a video camera capable of high-speed shooting at 1 Mfps, the number of recording frames is only about 100 to 300. Therefore, in order to capture a momentary phenomenon with a high-speed video camera, it is important to accurately grasp the time of occurrence of the phenomenon and record a captured image at that time. For this reason, high-speed video cameras usually perform shooting according to the following procedure.
(1) Start shooting and record the image of each frame.
(2) When the number of recorded images exceeds the storage capacity of the video camera, the past images are deleted and new images are recorded.
(3) Repeat (2) until an external stop signal (trigger signal) is detected.
(4) If determined in advance, (2) is repeated for a predetermined time (number of sheets) within the recording capacity range even after the stop signal is detected.
(5) Stop shooting.

  In order to correctly capture an instantaneous phenomenon as described above, it is necessary to appropriately generate a stop signal corresponding to the phenomenon.

  When the metal undergoes the phase transformation as described above, if the surface of the metal is mirror-polished in advance, a pattern corresponding to the structure after transformation is often generated on the surface by the phase transformation. For example, in the case of the aforementioned martensitic transformation in carbon steel, the mirror surface changes to a needle-like pattern peculiar to the martensite phase. Therefore, it is conceivable to analyze the image while photographing the sample surface and generate a stop signal based on the result (image change). However, with the current technology, the image analysis speed is faster than the phase transformation speed. Too slow and impractical.

  Therefore, a light source (detection light source) for detecting a target phenomenon is provided separately from the photographing light source, and a stop signal is generated by detecting a change in the intensity of reflected light from the sample surface of the light (detection light). It is known to generate. In the case of the above example, the reflectivity of the sample surface changes due to the appearance of the martensite phase pattern on the mirror-finished surface accompanying the phase transformation, so it is stopped by detecting the reflected light of the detection light from the sample surface. A signal can be generated. A monochromatic light source such as a laser is often used as the imaging light source and a white continuous light source as the detection light source.

JP 2012-156805 JP

Kondo, 5 others, "Development of High-Speed Video Camera HyperVision HPV-1", Shimazu Review, Shimazu Review Editorial Department, September 2005, Vol. 62, No. 1, No. 2, pp. 79-86 Kondo, 5 others, "High-speed video camera HPV-2 and high-speed shooting application", Shimazu review, Shimazu review editorial department, March 2009, Volume 65, No. 3, No. 4, pp. 219-227

  In shooting with a high-speed video camera, since the exposure time of each image is short, it is necessary to sufficiently increase the light amount of the shooting light source. Furthermore, when photographing the above-mentioned metal phase transformation, the structure needs to be magnified on the order of a microscope (several tens to several hundreds times), and the amount of light entering the camera is small, so a more sufficient amount It is necessary to irradiate the object with the light.

  Such light for photographing (photographing light) becomes background noise for the light detection element of the detection light. In addition, when imaging the metal phase transformation as described above, it is necessary to heat the sample to near 1000 ° C, but the radiation (infrared, visible light, etc.) from the heated sample is also detected as noise. Comes in the element. In addition to the detection light, these noises are superimposed on the light detection element for generating the stop signal. However, when imaging the phase transformation of a metal sample, the change in the reflectance of the sample surface due to the phase transformation is large. Therefore, such a change is buried in noise, and it becomes difficult to generate a correct detection signal (stop signal).

  The problem to be solved by the present invention is to eliminate various noises, detect detection light with a higher S / N ratio, generate a stop signal, and correctly capture a high-speed phenomenon. It is to provide a speed shooting system.

The thing of the 1st aspect of the high-speed imaging system based on this invention made in order to solve the said subject is as follows.
a) a photographic light source that emits photographic light to be irradiated on an object by an external signal;
b) a camera for photographing the object;
c) a detection light source that emits detection light for generating a stop signal that irradiates the object;
d) a detector for detecting the detection light from the object by an external signal;
e) a control unit that controls the light so that the photographing light is emitted only during the exposure period of the photographing camera and the detector does not perform detection during the light emission period of the photographing light. .

In the high-speed imaging system according to the first aspect of the present invention, the control unit detects the exposure period based on a signal from the imaging camera and emits the imaging light only during the exposure period. To control. For this reason, photographing light can be made into powerful light.
The control unit controls the detector so that detection light is not detected during the emission period of the photographing light. Accordingly, since the detector does not detect strong photographing light when detecting the detection light, the detection light with less noise can be detected, and the stop signal can be generated more accurately. In the high-speed imaging system of this aspect, since the detector does not input strong imaging light during detection, a relatively weak continuous light source can be used as the detection light source. Of course, a light source that emits light only at the time of detection may be used.

The second aspect of the high-speed photographing system according to the present invention made to solve the above problems is as follows:
a) a photographic light source that emits photographic light irradiating the object;
b) a camera for photographing the object;
c) a detection light source that emits detection light for generating a stop signal to irradiate the object by an external signal;
d) a detector for detecting the detection light from the object;
e) a control unit that controls the light source for detection so as not to emit light during the exposure period of the camera for photographing.

In the high-speed imaging system according to the second aspect of the present invention, the control unit detects the exposure period based on the signal from the imaging camera and controls the detection light source so as not to emit light during the exposure period. To do. Therefore, a powerful light source can be used as the detection light source, and the detector can detect detection light with relatively little noise. Thereby, a stop signal can be generated more accurately.
In the high-speed imaging system of this aspect, no detection light is emitted during the exposure period, so that the detection light does not interfere with imaging. Therefore, a relatively weak continuous light source can be used as the imaging light source.

In any high-speed imaging system, it is desirable to select a laser beam having a wavelength different from the wavelength component included in the imaging light or the heat ray of the sample as the detection light.
In addition, it is desirable to remove, with a notch filter (band elimination filter), a wavelength component equal to (and close to) the detection light among the wavelength components included in the imaging illumination before the imaging light source.
Furthermore, it is desirable to narrow the band of the photodetector element of the detector with a bandpass filter.
These additional measures further improve the detection accuracy of the detector.

  In the high-speed imaging system according to the present invention, since the S / N ratio in the detector for generating the stop signal can be increased in any aspect, the stop signal is generated with high accuracy, and the high-speed The phenomenon can be correctly photographed.

1 is a schematic configuration diagram of a high-speed imaging system that is an embodiment of the present invention. The control block diagram of the high-speed imaging system of an Example. The timing chart of the high-speed imaging | photography of the 1st aspect by the high-speed imaging | photography system of an Example. The timing chart of the high-speed imaging | photography of the 2nd aspect by the high-speed imaging | photography system of an Example.

  A high-speed imaging system for detecting a phase transformation of steel, which is an embodiment of the present invention, will be described. As shown in FIG. 1, the high-speed photographing system 10 is a high-temperature photographing chamber 12 for heating and cooling a steel sample 11, and a high-speed photographing sample 11 through a window (not shown) provided in the conditioning chamber 12. The speed camera 13, the imaging light source 14 that irradiates the sample 11 with imaging light, the detection light source 15 that irradiates the sample 11 with timing detection light (detection light), and the detection light reflected on the surface of the sample 11 are detected. Based on the detector 16 and a signal from the detector 16, a timer 17 that determines the stop timing of high-speed shooting and gives a stop signal to the high-speed camera 13 is provided. An optical bandpass filter 18 that allows only the detection light of the detector 16 to pass is provided in front of the detector 16. Further, although not shown, it is desirable to provide a notch filter (band elimination filter) that removes only the detection light of the detector 16 in front of the imaging light source 14.

  As shown in FIG. 2, in the high-speed imaging system 10 of the present embodiment, a control unit 24 is included in the high-speed camera 13. The control unit 24 takes out the image data from the image memory (IMG) 22 that stores the image data generated by the image pickup device 21 and controls the operation thereof, as well as the photographing light source 14, the detection light source 15, and the detector 16. Signals are exchanged with the timer 17 and the like via the interface (I / F) 23, and their operations are controlled and information is received from them.

  Next, operation | movement of this high speed imaging | photography system 10 at the time of imaging | photography the mode of the phase transformation of the sample 11 which is steel is demonstrated. By polishing one surface of the sample 11 into a mirror surface in advance and photographing the surface with the high-speed camera 13, the temperature of the sample 11 is increased (or decreased), so that the steel can be phased at a certain temperature. Transformation occurs, and the surface of the sample 11 changes from a mirror state to a state in which a structure (pattern) corresponding to the generation phase appears. Since the speed of this change (transformation) is very high, it is necessary to shoot with the high-speed camera 13, but the high-speed camera 13 has a short exposure time for each frame and a small amount of photographic light. In addition, since the structure that appears due to the phase transformation of steel is fine, the high-speed camera 13 must shoot the surface of the sample 11 with an imaging field width of about 0.5 mm, and obtain from that field of view. The amount of light emitted is even less. For this reason, it is necessary to sufficiently increase the amount of light that the imaging light source 14 irradiates the sample 11. However, since it is difficult to generate such a large amount of light by continuous light emission, the imaging light source 14 is used as a pulsed light source here. On the other hand, a continuous light source is used as the detection light source 15.

  FIG. 3 shows the timing of frame shooting (exposure) of the high-speed camera 13, light emission of the shooting light source 14, and detection of the detector 16 when such a system is configured. The high-speed camera 13 performs exposure for a predetermined exposure time at a predetermined interval, and collects image data of each frame. Based on the exposure timing signal of the high-speed camera 13, the control unit 24 outputs a light emission signal to the photographing light source 14 only during the exposure time. As a result, the imaging light source 14 irradiates the sample 11 with powerful pulsed imaging light. The control unit 24 further sends a detection timing signal to the detector 16 so that no detection is performed during the period of emission of the photographing light. The detector 16 detects the detection light in accordance with the detection timing signal and sends the detection signal to the timer 17. The timer 17 compares this detection signal with a predetermined reference level, generates a stop signal when it becomes lower than the reference level, and sends it to the high-speed camera 13. When receiving the stop signal, the control unit 24 of the high-speed camera 13 stops further accumulation of image data in the image memory 22. As a result, the image memory 22 holds the image data from the time point to the time point that is traced back a predetermined time, and the state of the surface change during the phase transformation of the sample 11 is photographed.

  As described above, in the high-speed imaging system 10 of the present embodiment, the detector 16 does not perform detection while strong imaging light is emitted, so that the S / N ratio of detection in the detector 16 is increased, and the timer No. 17 can more appropriately determine the stop timing.

Next, another embodiment using the high-speed imaging system 10 of the present embodiment will be described. When the tissue appearing on the surface of the sample 11 is large and sufficient imaging is possible without enlarging, a continuous light source with a relatively low light quantity can be used as the imaging light source 14. On the other hand, when the temperature of the phase transformation to be observed is high, thermal radiation from the sample 11 itself becomes large, and therefore radiation from the sample 11 (infrared rays and visible light) becomes a problem as noise in the detector 16. Come. Therefore, in this embodiment, in order to increase the S / N ratio in the detector 16 by increasing the light amount of the detection light, a pulse laser light source capable of emitting a strong light amount is used as the detection light source 15. In this case, as shown in FIG. 4, the control unit 24 prevents the detection light source 15 from emitting light during the exposure period of the high-speed camera 13 and prevents the detection light from interfering with photographing.
Thus, in this embodiment, since the detection light does not interfere with the photographing, it is possible to use a strong detection light, the S / N ratio of detection in the detector 16 is increased as described above, and the timer 17 is appropriately stopped. The timing can be judged.

  In any of the above-described high-speed imaging systems, it is desirable to select light having a wavelength different from the wavelength component included in the imaging light or the heat rays of the sample as the detection light.

DESCRIPTION OF SYMBOLS 10 ... High-speed imaging system 11 ... Sample 12 ... Conditioning room 13 ... High-speed camera 14 ... Imaging light source 15 ... Detection light source 16 ... Detector 17 ... Timer 18 ... Optical band pass filter 21 ... Image sensor 22 ... Image memory (IMG)
23 ... Interface (I / F)
24 ... Control unit (CONT)

Claims (7)

a) a photographic light source that emits photographic light to be irradiated on an object by an external signal;
b) a camera for photographing the object;
c) a detection light source that emits detection light for generating a stop signal that irradiates the object;
d) a detector for detecting the detection light from the object by an external signal;
e) a control unit that controls the light so that the photographing light is emitted only during the exposure period of the photographing camera and the detector does not perform detection during the light emission period of the photographing light. High-speed shooting system.   The high-speed imaging system according to claim 1, wherein the detection light source continuously emits the detection light. a) a photographic light source that emits photographic light irradiating the object;
b) a camera for photographing the object;
c) a detection light source that emits detection light for generating a stop signal to irradiate the object by an external signal;
d) a detector for detecting the detection light from the object;
e) a high-speed photographing system comprising: a control unit that controls the light source for detection so that light emission is not performed during an exposure period of the photographing camera.   The high-speed photographing system according to claim 3, wherein the photographing light source continuously emits the photographing light.   The high-speed imaging system according to claim 1, wherein the detection light is light having a wavelength different from that of the imaging light.   The high-speed imaging system according to claim 1, wherein a band elimination filter that removes a wavelength component of detection light is provided in front of the imaging light source.   The high-speed imaging system according to claim 1, wherein a band-pass filter that allows only detection light to pass is provided in front of the detector.

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