JPH0514790A - Television camera for flow velocity measuring system - Google Patents

Abstract

PURPOSE:To obtain a picture signal for a flow velocity measurement without setting a complicated optical system. CONSTITUTION:An optical system 2 for forming the same visual field is provided on two CCD image pickup elements 7 and 8. The exposure timing of each image pickup element is independently controlled by an exposure control means 10, and either one of video signals V1 and VS2 obtained based on an output from each image pickup element is delayed by a delay means 18 only by one field operating time. This delayed video signal is selectively synthesized with the other video signal by a signal synthesizer 19, and a synthesized video signal OS necessary for the flow velocity measurement can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television camera for a flow velocity measuring system, and more specifically, it visualizes a flow field by using a tracer to measure the flow velocity of the flow field. The present invention relates to a television camera suitable for a system that measures flow velocity using a video signal related to an image.

[0002]

2. Description of the Related Art For example, a method of visualizing a flow field by injecting a tracer into the fluid is known in order to know the flow velocity distribution of the flow field created by the flow of the fluid in a passage.
In order to obtain the flow velocity information in the flow field visualized in this way as data of quantitative distribution, the state of this visualized flow field is converted into a video signal using an interlaced television camera, With respect to the obtained image data, two frame images were created from each field image in the frame image, and the trace image formed by the same tracer in each image was obtained by the thinning process. A method has been proposed in which the flow velocity distribution is estimated from the amount of movement between two frame images of the trace image formed by the same tracer, which is estimated from the information on the tilt angle and length of the thin line (visualization of the flow , Vol.9, No.34, pp. 379-382
page). Since this method handles only one frame of television image, it has a feature that its application range is wider than the method of handling two or more frames of television image. However, in the above-mentioned conventional method, since the inclination angle and the length are obtained from the thinning processing result of the trace image, and the trace image is estimated using this result, the tracking noise is added to the image. When superposed, there is a problem that the tracking processing result is greatly affected by noise and causes a large error in the flow velocity measurement result. In order to reduce this error, in order to visualize the flow, a good illumination state is an essential requirement, and the particle size of tracer particles must be selected and used within a certain range. This is because the length of the thin line after the thinning process of the trace images of particles with different particle diameters is
The reason is that even if the lengths of the trace images are the same, the results will be different. Therefore, there is a problem that these points must be overcome in order to put the above-mentioned conventional technique into practical use. Therefore, as a flow velocity distribution measurement system that can reduce the influence of noise and measure the flow velocity distribution state more accurately, a visualized flow field is used by using a television camera of an interlaced scanning camera tube system without a shutter. A configuration has been proposed in which the correspondence relationship between the trace images between the field image data is determined by taking a picture and performing a logical product operation of the field image data forming one frame of the television image signal obtained thereby. .. However, in this proposed system, the measurement time is NT
Due to the restriction of the SC system television image sampling period, and in the vidicon television camera, when the moving speed of the particles in the angle of view is fast, an error occurs in the particle trace image length. In the case of, there is a problem that measurement is difficult.

[0003]

In order to solve the above-mentioned problems in the prior art, for example, when a flow field visualized by two CCD shutter type image pickup devices is photographed,
Paying attention to the fact that the image data showing the tracer movement trajectory while the shutter is open is obtained from each imaging device.
In one CCD shutter type image pickup device, each trace image shown by the image data from one image pickup device is controlled by changing the shutter opening timing and controlling the exposure times to overlap. Between the trace images shown by the image data from the other image pickup device and the trace images shown by the image data from the other image pickup device, the images are overlapped by the amount corresponding to the overlapping exposure time, and the movement traces of the same tracer particles are detected in these one set of images. By utilizing the principle that each trace image shown will have an overlapping part corresponding to the overlapping exposure time by overlapping the images, by finding the overlap between the trace images in each image, In, it is conceivable to associate the trace images with the same tracer particles. However, when attempting to analyze the flow velocity distribution and the like by such a method, it is necessary to set the optical system so that the fields of view of at least two TV cameras are the same. However, there is a problem in that it requires time and labor. The object of the present invention is therefore to make it possible to measure fast flows without the above-mentioned disadvantages, and to make it easy for anyone to obtain the necessary signals without complicated settings. I chose
It is to provide a television camera for a flow velocity measurement system.

[0004]

The feature of the present invention for achieving the above object is to measure a two-dimensional flow velocity of a flow field based on a television image signal of the flow field visualized by injecting a tracer. A television camera for use in operating the first and second CCD image pickup devices and the first and second CCD image pickup devices at the same time by capturing the visualized desired flow field from a predetermined visual field. An optical system for forming the same optical image, an exposure control means for independently controlling the exposure timings of the first and second CCD image pickup devices, and an exposure control means for controlling the exposure timing of the first and second CCD image pickup devices. Video signal output means for outputting the first and second video signals in response to each exposure output, and for obtaining the delayed first video signal by delaying the first video signal by one field scanning time Delay means, responsive to the second video signal and the delayed first video signal, selectively synthesize the field signals of the second video signal and the field signals of the delayed first video signal to produce a synthesized video signal. And a signal synthesizing means for outputting.

[0005]

By the optical system, exactly the same required field image is formed on the first and second CCD image pickup devices, and this field image is exposed for the shutter time determined by the exposure control means. The first video signal, which is one of the resulting first and second video signals, is delayed from the second video signal, which is the other video signal, by a time corresponding to one field scanning time. .. As a result, the delayed first video signal delayed by one field scanning time from the second video signal is obtained. The signal synthesizing means synthesizes the odd field component of the delayed first video signal and the odd field component of the second video signal, or the even field component of the delayed first video signal and the even field component of the second video signal, for example. Can be combined, and a video signal composed of the combined frame signals can be output as a combined video signal.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a video camera 1 according to the present invention. An optical system 2 includes a lens 3 having a long back focus, an infrared filter 4, and 1 :.
A cube half mirror 5 of No. 1 and a mirror 4 are arranged as shown in the figure, and a field image of a subject (not shown) in a predetermined field of view is obtained by the lens 3.

The field-of-view image is transmitted through the half mirror 5 to the first CC
A field image is formed on the D image pickup device 7 and also on the second CCD image pickup device 8 by the half mirror 5 and the mirror 6. That is, as can be seen from FIG. 1, substantially the same visual field images are formed on the first and second CCD image pickup devices 7 and 8.

To control the exposure time in the first and second CCD image pickup devices, an exposure control circuit 10 for controlling the shutter in response to the time base signal TB from the signal generator 9 is provided. In the exposure control circuit 10, 11 is a first control signal generation circuit that outputs a first control signal R1 for determining the exposure timing of the first CCD image pickup device 7, and 12 is a first control signal generation circuit for determining the exposure timing of the second CCD image pickup device 8. A second control signal generation circuit that outputs a second control signal R2, and a first CC that responds to the first control signal R1
The first shutter circuit for determining the exposure timing of the D image pickup device 7, that is, the shutter timing, and the second shutter circuit 14 for determining the exposure timing of the second CCD image pickup device 8, that is, the shutter timing, in response to the second control signal R2.
It is a shutter circuit.

As can be seen from the above description, the exposure control circuit 1
0 can independently control the exposure of the first and second CCD image pickup devices 7 and 8, and the first image pickup signal F1 from the first shutter circuit is input to the first video circuit 15.
The second image pickup signal F2 from the second shutter circuit 14 is input to the second video circuit 16.

The synchronization signal generating circuit 17 has a second control signal R
2 is a circuit for generating a sync signal necessary for forming an NTSC video signal in response to the step 2. The sync signal SY from the sync signal generation circuit 17 is supplied to the first and second video circuits 15 and 16. Each has been entered. The first and second video circuits 15 and 16 receive the input image pickup signals F1 and F, respectively.
2 is a known circuit for outputting the corresponding NTSC system first video signal VS1 and second video signal VS2 based on H.2.

The first video signal VS1 is a delay circuit 18 to which the time base signal TB and the synchronizing signal SY are input.
Where a delay time of 1 field scanning period, that is, 1/60 seconds, is given to the first video signal VS.
Delayed first video signal D delayed by 1/60 seconds from 1
VS1 is output.

The delayed first video signal DVS1 and the second video signal VS2 are input to the synthesizing circuit 19, where the odd field signal component of the delayed first video signal DVS1 and the corresponding odd field of the second video signal VS2. An odd frame signal which is combined with the signal component to form one frame, or an even field signal component of the delayed first video signal DVS1 and the corresponding second video signal V
The even field signal of S2 is combined to obtain one of the even frame signals forming one frame, and these signals are output to the output terminal 20 as the combined video signal OS.
Is output to.

A detailed block diagram of the delay circuit 18 is shown in FIG.

Describing the delay circuit 18, the first video signal VS1 to be delayed is the sync signal separation circuit 2.
1, the sync signal is separated therefrom, and the image signal S1 from which the sync signal is removed is input to the analog-digital converter (A / D) 22. Reference numeral 23 indicates that the clock pulse C is obtained by dividing the time base signal TB.
It is a frequency dividing circuit that outputs K, and the analog-digital converter 22 receives this clock pulse CK,
The input image signal S1 which is an analog signal is converted into a digital signal and output as a digital image signal DS1.

The digital image signal DS1 is a synchronizing signal S
It is input to the switch circuit 24 which operates in response to the vertical synchronizing signal VSY included in Y. Switch circuit 2
4 is a configuration in which each time a vertical synchronizing pulse of the vertical synchronizing signal VSY is input, the input signal is switched to output from an output opposite to the output 24a or 24b which has been output until then. .. In the illustrated embodiment, the switch circuit 24 is configured so that the odd field signal is output to the output line 24a and the even field signal is output to the output line 24b, and the odd field signal is randomly accessed. Memory (RAM) 25
Input / output unit (I / O) 25a, and the even field signal is input to the input / output unit 26a of the random access memory (RAM) 26.

A counter 27 is provided which counts clock pulses CK and is reset by the vertical synchronizing signal VSY in order to generate address data for writing and reading in the RAMs 25 and 26. The data indicating the count value of the counter 27 is the RAM as the address data AD.
25 and 26, the digital signal DS1 input from the switch circuit 24 is stored at the address designated by the address data AD.

The digital image signal DS1 stored in the RAMs 25 and 26 as described above is the vertical synchronizing signal VS.
It is read out alternately in response to Y, and the corresponding input / output unit 25
It is input to the switch circuit 28 via a and 26a. Each time the vertical synchronizing signal VSY is input, the switch circuit 28 alternately selects the signal applied to either one of the inputs 28a and 28b, and the selected signal responds to the clock pulse CK. It is converted into a corresponding analog signal in a digital-analog converter (D / A) 29 which operates as a unit.

The output from the digital-analog converter 29 is input to the sync signal adding circuit 30 to which the sync signal SY is input, and the required sync signal is added to the NTSC signal.
It is used as a system video signal. This signal is sent by the RAMs 25 and 26 for one field scanning time, that is, 1 /
Since the delay time of 60 seconds has been given, the delayed first video signal DVS1 is output.

As described above, in this embodiment, the switch circuit 24 uses the vertical synchronizing signal to output the first video signal VS1.
The odd field signal component and the even field signal component of are separated and stored alternately in the RAMs 25 and 26,
After 60 seconds, the data in the RAMs 25 and 26 are alternately taken out, returned to the original state by the switch circuit 28, a required synchronization signal is added, and 1 / th of the first video signal VS1 is added.
The delayed first video signal DVS1 delayed by 60 seconds can be obtained. But this required delay is
It goes without saying that the configuration may be realized by using another appropriate circuit or the like instead of the configuration shown in FIG.

FIG. 3 is a block diagram showing the configuration of the synthesizing circuit 19, which has an analog switch 31 for selecting either the delayed first video signal DVS1 or the second video signal VS2. As a signal for switching control of the analog switch 31, a Q output of a flip-flop 32 that operates in response to the vertical synchronizing signal VSY is given, and Q is applied every time a vertical synchronizing pulse of the vertical synchronizing signal VSY is applied.
When the output level is inverted and the Q output level is "H", the delayed first video signal DVS1 is selected, and when the Q output level is "L", the second video signal VS2 is selected. Therefore, when the analog switch 31 alternately takes out the odd field signal component of the delayed first video signal DVS1 and the odd field signal component of the second video signal DVS2, an odd frame signal is obtained, which is the composite video signal. Become. Also, analog switch 3
According to 1, when the even field signal component of the delayed first video signal DVS1 and the even field signal component of the second video signal DVS2 are alternately taken out, an even frame signal is obtained, and this becomes a composite video signal. Whether to take out the odd-numbered frame signal or the even-numbered frame signal can be easily determined by, for example, appropriately selecting the initial setting state of the flip-flop 32. One of the video signals selected by the analog switch 31 is taken out as a composite video signal via the output circuit 33.

Next, the operation of the video camera 1 will be described with reference to FIGS. 4 and 5.

The video camera 1 is a CCD shutter type camera, and the first control signal R1 and the second control signal R2 for shutter control are as shown in FIGS. 4 (a) and 4 (b), respectively. The shutter is controlled so that the common exposure timing is generated although the exposure timing is shifted.

In the illustrated embodiment, the first control signal R1 is an "H" level at time t = t0, and is an "L" level at time t = t1 after a lapse of time T1, from which t0 <t. The shutter of the first CCD image pickup device 7 is controlled to be in the open state only for the period of <t1.

On the other hand, the second control signal R2 becomes the "H" level at the time t = t0, and after the time T1 has elapsed, the second control signal R2 still maintains the "H" level state at t = t1,
Is a signal that becomes the “L” level at t = t2 when a time T2 has elapsed from = t1. As a result, the shutter of the second CCD image pickup device 8 is released only during the period of t0 <t <t2.

As can be seen from the above description, both the first and second CCD image pickup devices 7 and 8 are exposed during the time T1 from t0 to t1, but the second CCD image pickup device 8 is
Further, the time T2 from t1 to t2 is also in the exposure state. That is, the exposure timings of the CCD image pickup devices 7 and 8 are set to be temporally shifted and include a common exposure timing (t0 <t <t1).

Of the two first and second video signals VS1 and VS2 having such a relationship, the first video signal VS1
Is delayed by 1/60 seconds by a delay circuit 18, and an odd field signal component or even field signal component of two video signals having a time shift of 1/60 second is combined by a combining circuit 19. Are combined into a one-frame video signal.

As a result, by using this video camera 1, a fluid flow velocity distribution measuring system 50 as shown in FIG. 3 can be constructed.

The measuring system 50 measures the flow field of the fluid 52 visualized by injecting appropriate tracer particles 53 such as particles of nylon 12 into the fluid 52 in the water tank 51 made of transparent glass. It is a system for. In the video camera 1, the visualized flow field is viewed in the same field of view and at the exposure timing shown in FIG.
Two video signals VS1 and V that are displaced as shown in FIG.
S2 is made first. These signals are two image data showing the trace image of the tracer 52.

In the video camera 1, the composite video signal which can read the change of the trace image from the two video signals VS1 and VS2, that is, the above-mentioned odd frame signal or even frame signal is composed video signal OS. Is output as.

The composite video signal OS is stored in the computer 54.
To the fluid 52 by calculating the movement vector of each barycentric position of the trace image in the trace image indicated by each frame signal of the synthetic video signal OS by the analysis program input to the memory 55. A two-dimensional flow velocity distribution can be calculated.

[0032]

According to the present invention, two field video signals obtained at appropriate exposure timings can be obtained on the same CCD video camera and combined into one frame video signal. When a video camera is used, the setting of an optical system which requires the skill required for obtaining the same field of view becomes unnecessary, and an image recording device at the time of off-line measurement such as a video tape recorder. Also one is enough,
Image management during playback is also extremely easy because no frame matching is required.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video camera according to the present invention.

FIG. 2 is a detailed block diagram of the delay circuit shown in FIG.

FIG. 3 is a detailed block diagram of the synthesis circuit of FIG.

4 is a waveform diagram for explaining the operation of the video camera of FIG.

5 is a schematic configuration diagram showing an example of a fluid velocity distribution measuring system configured using the video camera of FIG.

[Explanation of symbols]

 1 Video Camera 2 Optical System 7 First CCD Image Sensor 8 Second CCD Image Sensor 10 Exposure Control Circuit 15 First Video Circuit 16 Second Video Circuit 18 Delay Circuit 19 Synthesis Circuit F1 First Image Signal F2 Second Image Signal VS1 First Video Signal VS2 Second video signal DVS1 Delayed first video signal OS Composite video signal

Claims (1)

Claim: What is claimed is: 1. A television camera for use in measuring a two-dimensional flow velocity of a flow field based on a television image signal of the flow field visualized by injecting a tracer. , An optical for capturing the same desired optical image on the first and second CCD image pickup devices and the first and second CCD image pickup devices at the same time by capturing the visualized desired flow field in a predetermined visual field. System and the first and second CCs
Exposure control means for independently controlling the exposure timing of the D image pickup device, and video signal output means for outputting the first and second video signals in response to the respective exposure outputs from the first and second CCD image pickup devices. A delay means for delaying the first video signal by one field scanning time to obtain a delayed first video signal, and a delay means for responding to the second video signal and the delayed first video signal. A television camera for a flow velocity measuring system, comprising: a signal synthesizing unit that selectively synthesizes each field signal and each field signal of the delayed first video signal to output a synthesized video signal.