JP5318328B2 - Flow velocity measuring device - Google Patents

Description

  The present invention relates to a flow velocity measuring device that images a fluid such as a river and analyzes the fluid image to calculate the fluid velocity.

For example, when measuring the velocity of a fluid such as a river in a conventional flow velocity measuring device, a float serving as a mark is caused to flow through the river, and the velocity of the fluid is observed to calculate the velocity of the fluid (for example, a patent) Reference 1).
Therefore, in the conventional flow velocity measuring device, a device or equipment that floats on the river is required.

In addition to the flow velocity measuring device described above, a flow velocity measuring device has been developed that captures a river using a camera and analyzes the river image to calculate the fluid velocity (see, for example, Patent Documents 2 and 3). ).
In this flow velocity measuring device, a plurality of blocks having a predetermined width and height are arranged at regular intervals within the imaging range of the camera, and the original image (latest river image) and past image (constant image) in each block are arranged. Calculate the correlation of river images before time). The fluid velocity is calculated from the correlation calculation result of each block.
In this flow velocity measuring device, the speed of fluid is calculated by focusing on garbage floating in the river and moving objects such as bubbles and waves in the river. There is no need to install.

JP-A-8-43419 (paragraph numbers [0007] to [0012], FIG. 1) Japanese Patent Laid-Open No. 7-5188 (paragraph numbers [0006] to [0012], FIG. 1) JP 2003-84006 A (paragraph numbers [0026] to [0045], FIG. 3)

  Since the conventional flow velocity measuring apparatus is configured as described above, the velocity of the fluid can be accurately calculated if the block can be arranged in a region where a moving object may exist. However, it is only necessary to evenly arrange a plurality of blocks at regular intervals without determining the area where the moving object may exist. However, when there is no moving object in the block, there is a problem that the fluid velocity cannot be accurately calculated.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a flow velocity measuring device that can accurately calculate the velocity of a fluid without causing a floating mark to flow in a river or the like. To do.

The flow velocity measuring device according to the present invention includes a difference value calculating unit that calculates a difference value between the latest fluid image captured by the fluid imaging unit and a past fluid image stored in the image storage unit, and the difference value calculation. Effective area selection for arranging a plurality of effective blocks in which there is a possibility of moving objects within the measurement area set in the imaging range of the fluid imaging means, using the difference value calculated by the means as a criterion And a correlation calculation means for calculating the correlation between the latest fluid image in the effective block and the past fluid image for each of the plurality of effective blocks arranged by the effective area selection means, and the correlation calculation of the correlation calculation means The movement direction for each effective block is obtained from the result, and an effective block whose movement direction does not fall within the preset allowable range is effective as an unreliable effective block. Excluded from the plurality of valid blocks arranged by frequency selection unit, in which a flow rate calculating means for calculating a velocity of the fluid from the correlation calculation result according to the valid block is reliable.

According to the invention, without flowing the float to be eye mark rivers, there is an effect that can be accurately calculated the velocity of the fluid.
In addition, there is an effect that the calculation accuracy of the fluid velocity can be improved.

Embodiment 1 FIG.
1 is a block diagram showing a flow velocity measuring apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a block diagram showing the inside of an image processing apparatus in the flow velocity measuring apparatus according to Embodiment 1 of the present invention.
In the figure, a camera 1 is installed in, for example, a basin of a river to be observed, images a river that is a fluid at a set time, and transmits a video signal (video signal) indicating an image of the fluid to the image processing device 2. To implement. The camera 1 constitutes fluid imaging means.
The image processing apparatus 2 analyzes the video signal transmitted from the camera 1 and performs a process of calculating the fluid velocity.

The external I / F unit 11 of the image processing apparatus 2 accepts the setting of data (for example, measurement region F, threshold A, allowable angle θ, coefficients α, β, etc.) used when calculating the fluid velocity. When the calculated fluid velocity is faster than the warning value, a process such as notifying an alarm is performed.
The video signal input processing unit 12 of the image processing apparatus 2 takes in the video signal transmitted from the camera 1 and performs processing such as converting the video signal into digital image data.
The image memory 13 of the image processing apparatus 2 is a memory that stores the image data output from the video signal input processing unit 12 for a certain period. The image memory 13 constitutes image storage means.

The difference processing unit 14 of the image processing apparatus 2 uses the latest image data output from the video signal input processing unit 12 and the image data of a predetermined time saved in the image memory 13 to capture the current image. In addition, a process of calculating a difference value between luminance values of the latest fluid image and a past fluid image captured by the camera 1 last time is performed. The difference processing unit 14 constitutes a difference value calculation unit.
The edge processing unit 15 of the image processing device 2 uses the latest image data output from the video signal input processing unit 12 to perform processing for calculating the edge value of the latest fluid image captured by the camera 1 this time. The edge processing unit 15 constitutes an edge value calculation unit.

The block placement unit 16 of the image processing apparatus 2 uses the difference value calculated by the difference processing unit 14 and the edge value calculated by the edge processing unit 15 as a determination criterion, and the measurement area F received by the external I / F unit 11. In this range, a process of arranging a plurality of effective blocks in an effective area where there is a possibility of moving objects (for example, bubbles, waves, dust) is performed. The block placement unit 16 constitutes an effective area selection unit.
The correlation calculation unit 17 of the image processing device 2 performs a process of calculating the correlation between the latest fluid image and the past fluid image in the effective block for each of the plurality of effective blocks arranged by the block arrangement unit 16. The correlation calculation unit 17 constitutes a correlation calculation unit.

The flow velocity calculation unit 18 of the image processing apparatus 2 performs a process of calculating the fluid velocity from the correlation calculation result of the correlation calculation unit 17. The flow velocity calculation unit 18 constitutes a flow velocity calculation means.
The memory unit 19 of the image processing apparatus 2 stores the fluid velocity calculated by the flow velocity calculating unit 18 and the reason why the fluid velocity cannot be obtained when the fluid velocity cannot be obtained by the flow velocity computing unit 18. It is.
FIG. 3 is a flowchart showing the processing contents of the flow velocity measuring apparatus according to Embodiment 1 of the present invention.

Next, the operation will be described.
Prior to the calculation of the fluid velocity by the image processing apparatus 2, the user uses the external I / F unit 11 to calculate data used when calculating the fluid velocity (for example, measurement region F, threshold A, allowable An angle θ, coefficients α, β, etc.) are set (step ST1).
The camera 1 is installed, for example, in the river basin of the observation target, images a river that is a fluid at each set time, and transmits a video signal indicating an image of the fluid to the image processing device 2.
FIG. 4 is an example showing an image of a river taken by the camera 1, and a square in the image is a measurement region F for measuring a flow velocity.

The video signal input processing unit 12 of the image processing apparatus 2 takes in the video signal transmitted from the camera 1 (step ST2).
The video signal input processing unit 12 converts the video signal into a data format (digital image data) that can be handled by a subsequent processing unit or arithmetic unit, and stores the digital image data in the image memory 13. .

When the video signal input processing unit 12 stores the image data in the image memory 13, the difference processing unit 14 of the image processing apparatus 2 and the latest image data output from the video signal input processing unit 12 and the image memory 13 are processed. Is used to calculate the difference value of the luminance value between the latest fluid image captured this time by the camera 1 and the past fluid image previously captured by the camera 1.
That is, the difference processing unit 14 obtains the difference value S (x, y) by calculating the following equation (1), for example.
S (x, y) = | G (x, y) -I (x, y) | (1)
Where G (x, y) is the luminance value in the latest fluid image (x, y).
I (x, y) is a luminance value in the past fluid image (x, y). Since the image data indicating the past fluid image is not stored in the image memory 13 at the time of activation, the video signal is output twice. The difference value is calculated at the stage where the above is taken.

When the video signal input processing unit 12 stores the image data in the image memory 13, the edge processing unit 15 of the image processing device 2 uses the latest image data output from the video signal input processing unit 12. The edge value of the latest fluid image imaged this time by the camera 1 is calculated.
That is, the edge processing unit 15 obtains the edge value E (x, y), for example, by calculating the following equation (2).
E (x, y)
= Abs (G (x-1, y) + G (x + 1, y)
+ G (x, y-1) + G (x, y + 1) -G (x, y) * 4) (2)

The block arrangement unit 16 of the image processing device 2 calculates the difference value S (x, y) when the difference processing unit 14 calculates the difference value S (x, y) and the edge processing unit 15 calculates the edge value E (x, y). x, y) and edge value E (x, y) are used as criteria, and there are moving objects (for example, bubbles, waves, dust) within the measurement area F received by the external I / F unit 11. Select multiple effective areas that may have
That is, the difference value S (x, y) calculated by the difference processing unit 14 has a large value in a pixel having a large luminance change between the latest fluid image and the past fluid image, and is calculated by the edge processing unit 15. The edge value E (x, y) thus obtained has a large value when the luminance difference between adjacent pixels is large.
For this reason, it is considered that there is a high possibility that a moving object is present at a position where the difference value S (x, y) and the edge value E (x, y) are large. As shown in the following formula (3), a judgment reference value Judg (x, y) at each position in the measurement region F is calculated.
Judg (x, y) = α × S (x, y) + β E (x, y) (3)
Here, α and β are weighting factors set by the user. 0 ≦ α ≦ 1, 0 ≦ β ≦ 1

When the block placement unit 16 calculates the judgment reference value Judg (x, y) at each position in the measurement region F, the block placement unit 16 selects n pieces in order from the position where the judgment reference value Judg (x, y) is large. An effective block is arranged at the position (step ST3). FIG. 5 shows an example in which six effective blocks are arranged in the measurement region F.
The effective block is arranged so that the selected position is at the center, but when it overlaps with the adjacent effective block, the effective block at the position where the criterion value Judg (x, y) is smaller is shifted. The plurality of effective blocks are arranged so as not to overlap each other.

When the block arranging unit 16 arranges n effective blocks, the correlation calculating unit 17 of the image processing device 2 calculates the correlation between the latest fluid image and the past fluid image in the effective block for each effective block. (Step ST4).
That is, the correlation calculation unit 17 uses the correlation calculation method set by the user using the external I / F unit 11 (for example, a method using template matching, a method using optical flow), and the effective block By calculating the correlation between the latest fluid image and the past fluid image, the movement amount (Δx, Δy) (unit: pixel) and score (reliability) of the effective block are calculated as the correlation calculation result.
As a correlation calculation method, for example, when using template matching, for example, the following equation (4) is calculated.

式（４）における右辺は、有効ブロックのスコア（信頼度）を表しており、右辺のΣが最小になるときの値が有効ブロックの移動量を表している。
なお、有効ブロックのスコア（信頼度）が小さい程、相関演算結果の信頼性が高いと判断される。

The right side in Expression (4) represents the score (reliability) of the effective block, and the value when Σ on the right side is minimum represents the movement amount of the effective block.
Note that the smaller the score (reliability) of the effective block, the higher the reliability of the correlation calculation result.

When the correlation calculation unit 17 calculates the correlation between the latest fluid image and the past fluid image in each effective block, the flow velocity calculation unit 18 of the image processing device 2 is set by the user with the score (reliability) of each effective block. The threshold values A are compared to determine whether each effective block is a reliable block.
When the score (reliability) of the effective block is higher than the threshold A, the flow velocity calculation unit 18 recognizes that the block is not reliable, and selects the block from the n effective blocks arranged by the block arrangement unit 16. Are excluded (step ST5).

Further, the flow velocity calculation unit 18 determines the vector direction of the remaining effective blocks (focusing on the movement amounts (Δx, Δy) of the effective blocks), and whether the vector direction is within the range of the allowable angle θ set by the user. Determine whether or not.
When the vector direction of the effective block is not within the range of the allowable angle θ, the flow velocity calculation unit 18 recognizes that the block is not reliable and excludes the block from the remaining effective blocks (step ST6). ).

Next, the flow velocity calculation unit 18 of the image processing apparatus 2 performs unit conversion of the movement amount (Δx, Δy) (unit: pixel) of the remaining effective block (reliable effective block) (step ST7).
That is, the flow velocity calculation unit 18 converts the movement amount (Δx, Δy) (unit: pixel) of the effective block into a unit length (unit: cm) per pixel for each preset effective block.
For example, as shown in FIG. 6, when the horizontal width of the measurement region F is 100 pixels, if the upper side of the measurement region F is set to 200 cm and the lower side is set to 300 cm, the upper side is 2 cm / pixel and the lower side is 3 cm / pixel. Convert. Incidentally, the effective block arranged at the center (Y coordinate) of the measurement area F is converted to 2.5 cm / pixel.
On the image data, the near side (the lower side of the screen) generally appears larger, so the actual length per pixel is shorter than the rear side (the upper side of the screen). However, as described above, it is effective. Perspective correction is possible by converting the pixel length for each block.

なお、各有効ブロックを均等に扱うのではなく、信頼性が高い有効ブロックに大きな重みを付けるようにしてもよいし、また、最大、最小の有効ブロックを取り除いて平均値を求めるようにしてもよい。 When the velocity conversion unit 18 of the image processing apparatus 2 performs unit conversion of the movement amount (Δx, Δy) of the effective block, the unit conversion is performed by weighting the movement amount (Δx, Δy) of the effective block after the unit conversion. The movement amount of the measurement area F is calculated from the movement amount (Δx, Δy) of the subsequent effective block.
For example, when each effective block is treated equally, the average value of the movement amounts (Δx, Δy) of the effective blocks is calculated as the movement amount of the measurement region F as shown in the following formula (5), for example. .

Instead of treating each effective block equally, a large weight may be given to a highly reliable effective block, or the average value may be obtained by removing the maximum and minimum effective blocks. Good.

  When the flow velocity calculation unit 18 of the image processing apparatus 2 calculates the movement amount (unit: cm) of the measurement region F, the measurement region is calculated based on the imaging time difference (Δt) between the latest fluid image and the past fluid image used for the correlation calculation. By dividing the movement amount (unit: cm) of F, the surface flow velocity (unit: cm / s) in one process is calculated (step ST9). Hereinafter, the surface flow velocity in one treatment is referred to as “temporary flow velocity”.

Next, the flow velocity calculation unit 18 of the image processing device 2 determines that the calculation accuracy of the temporary flow velocity calculated as described above is low when the number of remaining effective blocks is smaller than the number set in advance by the user. Then, the calculation result of the temporary flow velocity is discarded, and that effect is recorded in the memory unit 19 (step ST10).
Further, the flow velocity calculation unit 18 obtains the ratio of the number of remaining effective blocks to the number of effective blocks arranged by the block arrangement unit 16, and when the ratio is smaller than the ratio set in advance by the user, It is determined that the calculation accuracy of the temporary flow velocity calculated in this way is low, the calculation result of the temporary flow velocity is discarded, and that effect is recorded in the memory unit 19 (step ST10).
Furthermore, the flow velocity calculation unit 18 also operates as described above even when the temporary flow velocity calculated as described above exceeds the upper limit speed set in advance by the user or lower than the lower limit speed set in advance by the user. It is determined that the calculation accuracy of the calculated temporary flow velocity is low, the calculation result of the temporary flow velocity is discarded, and that effect is recorded in the memory unit 19 (step ST11).

Next, when the flow velocity calculation unit 18 of the image processing apparatus 2 determines that the calculation accuracy of the temporary flow velocity calculated in the above manner is high, a preset number of effective temporary flow velocity (for example, a) (Temporary flow velocity) is determined within a preset time (step ST12).
When the a number of effective provisional flow speeds are obtained within a preset time, the flow rate calculation unit 18 calculates, for example, from a number of effective provisional flow speeds as shown in the following equation (6). The velocity of the fluid is finally calculated (step ST13).

なお、ａ個の有効な仮流速速度が予め設定された時間内に求められていない場合、前回最終的に算出された流体の速度を採用するようにしてもよい。 When a valid temporary flow velocity is not obtained within a preset time, for example, as shown in the following expression (7), the flow velocity calculation unit 18 determines M pieces obtained up to that point in time. The velocity of the fluid is provisionally calculated from the effective temporary flow velocity of (step ST14).

If a valid temporary flow velocity is not obtained within a preset time, the fluid velocity finally calculated last time may be adopted.

When the flow velocity calculation unit 18 of the image processing apparatus 2 finally or tentatively calculates the fluid velocity, the fluid velocity is recorded in the memory unit 19.
The flow velocity calculation unit 18 does not record the velocity of the flow velocity calculated this time in the memory unit 19 as it is, and the reliability when the velocity of the current fluid is calculated and the reliability when the velocity of the previous fluid is calculated. May be weighted, and the weighted result may be recorded in the memory unit 19.

Further, the flow velocity calculation unit 18 compares the speed of the fluid with an alarm value set in advance by the user (step ST15), and when the speed of the fluid is larger than the alarm value, the external I / F unit 11 is used. An alarm is notified to the outside (step ST16).
The alarm is notified, for example, by turning on an LED, sending a voice or buzzer, or sending a mail.

  As apparent from the above, according to the first embodiment, the difference processing unit 14 that calculates the difference value between the latest fluid image captured by the camera 1 and the past fluid image stored in the image memory 13. The edge processing unit 15 for calculating the edge value of the latest fluid image captured by the camera 1, the difference value calculated by the difference processing unit 14 and the edge value calculated by the edge processing unit 15 as a criterion. A block arrangement unit 16 for arranging a plurality of effective blocks in an effective area where a moving object may exist within the measurement area F received by the external I / F unit 11; For each of the plurality of effective blocks arranged by the block arrangement unit 16, the correlation between the latest fluid image and the past fluid image in the effective block is calculated, and the fluid calculation result is obtained from the correlation calculation result. Since it is configured to compute a degree, the float comprising a mark without flowing into rivers, an effect capable of accurately calculating the velocity of the fluid.

  Further, according to the first embodiment, with reference to the correlation calculation result of the correlation calculation unit 17, blocks having no reliability are excluded from a plurality of effective blocks arranged by the block arrangement unit 16, and reliability is improved. Since the fluid velocity is calculated from the correlation calculation result relating to a certain effective block, the fluid velocity calculation accuracy can be improved.

Further, according to the first embodiment, since the fluid velocity is smoothed in time series, the influence of a single erroneous computation result is reduced, and the fluid velocity computation accuracy is reduced. There is an effect that can be improved.
In addition, since a series of arithmetic processing is performed faster than the shape of features (bubbles, waves, etc.) on the surface of the fluid changes with time, high-precision and real-time flow velocity measurement can be performed. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the flow velocity measuring apparatus by Embodiment 1 of this invention. It is a block diagram which shows the inside of the image processing apparatus in the flow velocity measuring apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the flow velocity measuring apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows an example of the image of the river imaged with the camera. 6 is an explanatory diagram showing an example in which six effective blocks are arranged in a measurement region F. FIG. It is explanatory drawing explaining the unit conversion of the movement amount of an effective block.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Camera (fluid imaging means), 2 Image processing apparatus, 11 External I / F part, 12 Video signal input process part, 13 Image memory (Image storage means), 14 Difference processing part (Difference value calculation means), 15 Edge process Part (edge value calculation means), 16 block arrangement part (effective area selection means), 17 correlation calculation part (correlation calculation means), 18 flow velocity calculation part (flow velocity calculation means), 19 memory part.

Claims (4)

Fluid imaging means for imaging fluid at a set time;
Image storage means for storing an image of the fluid imaged by the fluid imaging means;
Difference value calculating means for calculating a difference value between the latest fluid image captured by the fluid imaging means and a past fluid image stored in the image storage means;
Using the difference value calculated by the difference value calculating means as a criterion, a plurality of effective blocks in which a moving object may exist within the measurement region set in the imaging range of the fluid imaging means Effective area selection means to be arranged;
Correlation calculation means for calculating the correlation between the latest fluid image in the effective block and the past fluid image for each of the plurality of effective blocks arranged by the effective area selection means;
The movement direction for each effective block is obtained from the correlation calculation result of the correlation calculation means, and the effective area is selected as an effective block having no reliability, if the calculated movement direction is not within the preset allowable range. A flow rate measuring device comprising: a flow rate calculating unit that excludes a plurality of effective blocks arranged by the unit and calculates a fluid velocity from a correlation calculation result related to a reliable effective block . Fluid imaging means for imaging fluid at a set time;
Image storage means for storing an image of the fluid imaged by the fluid imaging means;
Edge value calculating means for calculating the edge value of the latest fluid image imaged by the fluid imaging means;
Using the edge value calculated by the edge value calculating means as a criterion, a plurality of effective blocks in which a moving object may exist within the measurement region set in the imaging range of the fluid imaging means Effective area selection means to be arranged;
Correlation calculation means for calculating the correlation between the latest fluid image in the effective block and the past fluid image stored in the image storage means for each of the plurality of effective blocks arranged by the effective area selection means;
The movement direction for each effective block is obtained from the correlation calculation result of the correlation calculation means, and the effective area is selected as an effective block having no reliability, if the calculated movement direction is not within the preset allowable range. A flow rate measuring device comprising: a flow rate calculating unit that excludes a plurality of effective blocks arranged by the unit and calculates a fluid velocity from a correlation calculation result related to a reliable effective block . Fluid imaging means for imaging fluid at a set time;
Image storage means for storing an image of the fluid imaged by the fluid imaging means;
Difference value calculating means for calculating a difference value between the latest fluid image captured by the fluid imaging means and a past fluid image stored in the image storage means;
Edge value calculating means for calculating the edge value of the latest fluid image imaged by the fluid imaging means;
A moving object exists within the measurement area set in the imaging range of the fluid imaging means based on the difference value calculated by the difference value calculating means and the edge value calculated by the edge value calculating means as a criterion. Effective area selection means for arranging a plurality of effective blocks that may be,
Correlation calculation means for calculating the correlation between the latest fluid image in the effective block and the past fluid image for each of the plurality of effective blocks arranged by the effective area selection means;
The movement direction for each effective block is obtained from the correlation calculation result of the correlation calculation means, and the effective area is selected as an effective block having no reliability, if the calculated movement direction is not within the preset allowable range. A flow rate measuring device comprising: a flow rate calculating unit that excludes a plurality of effective blocks arranged by the unit and calculates a fluid velocity from a correlation calculation result related to a reliable effective block . The flow velocity measuring device according to any one of claims 1 to 3 , wherein the flow velocity calculation means smoothes the velocity of the fluid in time series.

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