Very Bad Image data

[Soccer Travel]

Hello, everyone!
It's difficult because it hasn't been long since I was in charge of the PIV experiment.
I don't know why there is very bad image data in the MATlAB
Which image is a good one?

Does anyone have any recommendations among the image samples I attached?

.

[William]

That doesnt look to bad (but your camera alignment is bad). The question is: How does your image PAIR look like? Is there a small enough delta t ?

[Soccer Travel]

Thank you for your response!
Here's a pair of images.
The Answer is: This image pair has a delta T of 100us.
The question is :How should I change the camera alignment?

2024년 7월 2일 화요일 오후 5시 29분 45초 UTC+9에 William님이 작성:

[William]

There is absolutely zero correlation between these images. Looks like they have been captured on two different days... Are you sure that your timing is right? What kind of equipment are you using? Is this water or air, and what is the approx. flow speed?

[Soccer Travel]

hello,,,

The equipment I'm using now is a double pulse laser, PCO1600 Camera, bubble generator, and pulse generator.
The current set period is 70 ms, but it appears to be 140 ms, which is double by the oscilloscope.

[Soccer Travel]

The ChA of the pulse generator is connected to the Camera Power supply,
ChC and ChD are connected to lasers 1 and 2, respectively.

Thank you for your assistance to me!!

[Soccer Travel]

The approximate average speed is around 0.4 m/s.

2024년 7월 3일 수요일 오전 11시 49분 23초 UTC+9에 Soccer Travel님이 작성:

[William]

Hi, I don't know your specific setup, I can only tell you that something with your timing is wrong, but I don't know how to fix it. From the numbers you have given, I think that the pulse separation (within an image pair) must be around 2 ms at 0.4 m/s flow speed and the magnification you are currently using. Then you will get an average displacement of approx. 5 pixels.

I am surprised that you run the Evergreen laser by only triggering the flashlamps. We have the same laser, and I am using our synchronizer to trigger L1, L2, Q1 and Q2 to get a precise timing. Maybe this is a limitation of your setup.

You should check your timing with an oscilloscope (use a photodiode or similar to see the actual emission of laserpulses, and check the "exposure active" signal of your camera.

And maybe consider checking out our simple PIV equipment that would be a perfect match for your current setup:

https://optolution.com/en/products/particle-image-velocimetry-piv/low-cost-piv-system-water/

[Soccer Travel]

Hello!
After seeing what you said, I succeeded in getting a correlated image pair by proceeding from the beginning again.
In the current setting, the delta T of the image pairs is set to 50us.
The current particle position between images A and B does not seem to be moving
In the next experiment, we will increase the delta T to 100us.

Can you give me some advice on the image?

For example, anything for a successful PIV experiment, such as particle size or focal microtime interval, is good.

Thank you always for your kind reply!!

2024년 7월 3일 수요일 오후 2시 36분 1초 UTC+9에 William님이 작성: